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Cybench: A Framework for Evaluating Cybersecurity Capabilities and Risks of Language Models
Andy K. Zhang, Neil Perry, Riya Dulepet, Joey Ji, Celeste Menders, Justin W. Lin, Eliot Jones, Gashon Hussein, Samantha Liu, Donovan Jasper, Pura Peetathawatchai, Ari Glenn, Vikram Sivashankar, Daniel Zamoshchin, Leo Glikbarg, Derek Askaryar, Mike Yang, Teddy Zhang, Rishi Alluri, Nathan Tran, Rinnara Sangpisit, Polycarpos Yiorkadjis, Kenny Osele, Gautham Raghupathi, Dan Boneh, Daniel E. Ho, Percy Liang
TL;DR
Cybersecurity language-model agents may identify vulnerabilities and execute exploits, creating a need to quantify their capabilities and risks. Cybench addresses this need with a benchmark of professional-level CTF tasks, subtasks, an executable agent environment, and evaluations across models and scaffolds. Without subtask guidance, several models solved tasks that human teams had solved in up to 11 minutes, while scaffolding effects varied by model.
Problem
Cybersecurity language-model agents can autonomously identify vulnerabilities and execute exploits, motivating benchmarks that quantify their capabilities and risks.
Method
Cybench specifies 40 recent professional-level CTF tasks with descriptions, starter files, evaluators, subtasks, and an executable Kali Linux agent environment, then evaluates models and agent scaffolds.
Results
Without subtask guidance, Claude 3.5 Sonnet, GPT-4o, OpenAI o1-preview, and Claude 3 Opus solved complete tasks with human first-solve times up to 11 minutes, while scaffolding effects were model-dependent.
Takeaways & Limitations
Cybench provides a framework for continuously evaluating cybersecurity agents as their capabilities and potential real-world impact develop.
Takeaways & Limitations
The released framework may accelerate development of stronger cybersecurity agents that could be leveraged by malicious actors to identify vulnerabilities and execute exploits on real systems.
Abstract
from arXiv · showhide
Language Model (LM) agents for cybersecurity that are capable of autonomously identifying vulnerabilities and executing exploits have potential to cause real-world impact. Policymakers, model providers, and researchers in the AI and cybersecurity communities are interested in quantifying the capabilities of such agents to help mitigate cyberrisk and investigate opportunities for penetration testing. Toward that end, we introduce Cybench, a framework for specifying cybersecurity tasks and evaluating agents on those tasks. We include 40 professional-level Capture the Flag (CTF) tasks from 4 distinct CTF competitions, chosen to be recent, meaningful, and spanning a wide range of difficulties. Each task includes its own description, starter files, and is initialized in an environment where an agent can execute commands and observe outputs. Since many tasks are beyond the capabilities of existing LM agents, we introduce subtasks for each task, which break down a task into intermediary steps for a more detailed evaluation. To evaluate agent capabilities, we construct a cybersecurity agent and evaluate 8 models: GPT-4o, OpenAI o1-preview, Claude 3 Opus, Claude 3.5 Sonnet, Mixtral 8x22b Instruct, Gemini 1.5 Pro, Llama 3 70B Chat, and Llama 3.1 405B Instruct. For the top performing models (GPT-4o and Claude 3.5 Sonnet), we further investigate performance across 4 agent scaffolds (structed bash, action-only, pseudoterminal, and web search). Without subtask guidance, agents leveraging Claude 3.5 Sonnet, GPT-4o, OpenAI o1-preview, and Claude 3 Opus successfully solved complete tasks that took human teams up to 11 minutes to solve. In comparison, the most difficult task took human teams 24 hours and 54 minutes to solve. All code and data are publicly available at https://cybench.github.io.
1 INTRODUCTION
Cybench addresses the need to measure cybersecurity capabilities and risks of language-model agents with a benchmark spanning professional-level CTF tasks, agent interaction, subtasks, and multiple models and scaffolds.
- Benchmark framework: Cybench is an open-source framework for specifying cybersecurity tasks and evaluating language-model agents on them.Each task includes a description, starter files, and an evaluator, while agents act in an executable environment and submit answers for verification.
- Subtask evaluation: Cybench uses subtasks to break difficult tasks into intermediary goals, enabling more granular evaluation when complete tasks exceed existing agents’ capabilities.Subtasks can separate stages such as identifying credentials, finding insecure code, crafting an exploit, and retrieving a secret.
- Benchmark tasks: The benchmark contains 40 recent professional-level CTF tasks from four competitions, spanning cryptography, web security, reverse engineering, forensics, exploitation, and miscellaneous skills.Tasks were selected to cover meaningful cybersecurity skills and a wide range of difficulties.
- Agent design: The evaluation agent executes bash actions in a Kali Linux environment, observes outputs, updates memory, and can use reflection, planning, status tracking, and thought.This interaction loop supports iterative cybersecurity-tool use before answer submission.
- Evaluation results: Across eight models, four models solved complete tasks corresponding to human first-solve times of up to 11 minutes without subtask guidance, while the hardest task took 24 hours and 54 minutes for humans.First solve time was also reported as a strong indicator of agent difficulty: most attempts succeeded at 11 minutes or below, whereas models failed above that threshold without subtasks.
- Evaluation results: Agent scaffolding effects were model-dependent: Claude 3.5 Sonnet outperformed, while GPT-4o underperformed, the structured bash scaffold with pseudoterminal and web search.The compared scaffolds included action-only responses, pseudoterminal interaction, and web search.
2 FRAMEWORK
Cybench specifies cybersecurity tasks with descriptions, starter files, evaluators, and executable environments, while subtasks provide partial-credit evaluation for complex objectives. Its agent runs an act–execute–update loop and can retain memory across subtasks.
- Task specification: Each task combines a textual goal, starter files, and an evaluator within an environment constructed for that task.Starter files may be local or remote, and the evaluator checks successful answers or unique success strings while tracking token and time usage.
- Environment: Agents interact with a Kali Linux container through bash commands, while remote task servers run in separate Docker containers on a shared network.The prompt supplies task-specific information such as hostnames and local files.
- Subtasks and metrics: Subtasks decompose complex cybersecurity tasks into discrete questions and answers, enabling partial credit beyond binary task success.Unguided performance is binary, whereas subtask performance is fractional according to the fraction of subtasks solved.
- Subtasks and metrics: Subtask-guided performance evaluates the final subtask, allowing comparison with unguided performance when the subtask goal matches the task goal.Memory is retained across subtasks, with optional additional context from previous subtasks.
- Agent-environment loop: The agent operates over time steps by producing a response and action, executing the action in the environment, then updating memory from the response and observation.Runs continue until an iteration limit or answer submission, with per-subtask limits in subtask mode.
3 TASK CREATION
Cybench constructs a broad, professionally grounded benchmark from 40 CTF challenges across four competitions and six cybersecurity categories. Task difficulty is anchored to human first solve time, while solution scripts and continuous integration improve task verifiability.
- Benchmark scope: Cybench includes 40 CTF tasks from four distinct competitions spanning cryptography, web security, reverse engineering, forensics, exploitation, and miscellaneous skills.The benchmark targets recent challenges that proxy real hacking skills, including vulnerabilities associated with actual CVEs.
- CTF challenges: CTF challenges require identifying vulnerabilities and executing exploits to retrieve a secret string called a flag, covering skills from web exploits to cryptography.Examples range from brute-forcing passwords and patching binaries to exploiting cryptographic flaws and performing return-oriented programming.
- Difficulty: First solve time provides human-grounded difficulty ratings ranging from 2 minutes to 24 hours and 54 minutes, a 747x increase.The benchmark exhibits approximately log-linear scaling in difficulty.
- Benchmark design: Each task includes a description, link, and log, and Cybench is designed as a deep and wide benchmark with annotated tasks, metadata, subtasks, categories, and varied difficulty.The benchmark is intended to grow over time and cover simple input-validation issues through complex return-oriented programming.
- Task verifiability: A solution script and continuous-integration checks verify that each task is buildable and solvable, while automated probes check that task servers are alive and accessible.This addresses challenges that may otherwise be too complex to build or solve reliably.
4 LM-BASED AGENT
The Cybench agent repeatedly acts from bounded memory, executes a parsed action in the environment, and updates memory with the resulting observation. Its structured response combines reflection, planning, thought, logging, and an executable action.
- Agent flow: The agent follows an act–execute–update loop in which memory guides action, execution produces an observation, and the observation updates memory.This loop is implemented at successive time steps in the task environment.
- Memory and action: At each step, the language model receives the initial prompt and the last three response–observation iterations, then produces a response whose parsed action is executed.The bounded memory is represented as a string passed to the language model as a prompt.
- Response structure: The response contains five fields: Reflection, Plan and Status, Thought, Log, and Action.Action is either a bash command or an answer submission.
5 EXPERIMENTS
The experiments evaluate eight language models and multiple agent scaffolds on Cybench, finding that performance depends on model, task difficulty, and scaffolding. Agents solve easier tasks but struggle sharply as first solve time increases, while limited training overlap supports the evaluation's validity.
- Experimental setup: Eight models are evaluated with structured bash agents, using unguided, subtask-guided, and subtask performance metrics.The experiments also compare action-only, pseudoterminal, and web-search scaffolds for top-performing models.
- Model capabilities: 17.5% is Claude 3.5 Sonnet's unguided performance and GPT-4o's subtask-guided performance, while OpenAI o1-preview reaches 46.8% subtask performance.Claude 3.5 Sonnet, GPT-4o, and OpenAI o1-preview lead on different metrics; GPT-4o solves a 52-minute-FST task with subtask guidance.
- Model capabilities: 73% of tasks with FST up to 11 minutes have non-zero unguided success, whereas no task above 11 minutes is solved.The most difficult task has an FST of 24 hours and 54 minutes, 136 times greater than 11 minutes.
- Model capabilities: More difficult tasks remain unsolved because their vulnerabilities require increasingly subtle insights, including multiple cryptographic steps in Robust CBC.Even subtask guidance for length-extension attacks does not enable a successful Robust CBC exploit.
- Evaluation caveats: Training-test overlap is minimal for solved tasks except those involving Claude 3.5 Sonnet, although its effect is difficult to determine.Nearly all successful runs concern tasks released after the relevant model knowledge cutoff.
- Agent scaffolds: Agent scaffolding effects are model-dependent: Claude 3.5 Sonnet benefits from pseudoterminal and web search, while GPT-4o performs worse than with structured bash.The authors interpret added expressivity as potentially increasing action-space complexity; reflection, planning, and thought generally outperform action-only prompting.
6 RELATED WORK
Cybench builds on cybersecurity, agent, and CTF benchmarks while distinguishing itself through professional-level tasks and objective difficulty grounded in competitor performance. Related work spans vulnerability exploitation, cybersecurity knowledge, agent environments, architectures, and offensive-security agents.
- CTF datasets: Existing CTF datasets include InterCode-CTF and the NYU CTF Dataset, but Cybench uses professional-level tasks and first solve time rather than subjective point-based difficulty.InterCode-CTF contains easier tasks, while NYU CTF difficulty is harder to compare directly.
- LM cybersecurity benchmarks: Other cybersecurity benchmarks assess vulnerability exploitation in code snippets or general cybersecurity knowledge through question answering.These benchmarks address narrower capabilities than full task-based cybersecurity evaluation.
- Agent benchmarks: Agent benchmarks such as AgentBench, InterCode, MLAgentBench, SWE-bench, WebShop, and WebArena evaluate agents across interactive environments and tasks.Cybench addresses the specialized environment and infrastructure requirements of cybersecurity tasks.
- Agent architectures: Prior agent-architecture research explores simulated-world memory, software-engineering platforms, multi-agent orchestration, and prompting methods.These approaches provide architectural and prompting precedents for cybersecurity agents.
- Offensive cybersecurity agents: Offensive-cybersecurity efforts include PentestGPT, HackingBuddyGPT, PenHeal, and related agents for penetration testing and CTFs.Cybench evaluates such agents against a unified benchmark of professional-level cybersecurity tasks.
7 CONCLUSION
The paper presents Cybench as a benchmark for evaluating cybersecurity agents across difficult tasks and varied scaffolds. It argues that continuous evaluation is needed because these agents are dual-use, and plans to expand the framework's architectures and task diversity.
- Contributions: Cybench combines recent, meaningful, difficult cybersecurity tasks with subtasks and four cybersecurity agent scaffolds.The benchmark is intended to support continued evaluation of agent capabilities.
- Implications: Cybersecurity agents can help developers identify bugs before deployment but may also help adversaries find exploits in deployed systems.The paper frames these capabilities as dual-use rather than exclusively defensive or offensive.
- Future work: The authors plan to update Cybench with new agent architectures and a more diverse set of tasks.This is the paper's stated direction for extending the framework.
- Caveat: The paper does not specify which version of Claude 3 was used.This limits reproducibility for that model's evaluation.
8 ETHICS STATEMENT
The authors weigh the dual-use risks and benefits of releasing Cybench, arguing that transparency, reproducibility, and defensive preparation support public release despite misuse concerns.
- Release risks: The released agent could help malicious actors identify vulnerabilities and execute exploits on real systems, although current agents cannot complete difficult cybersecurity tasks.The authors warn that improving LM capabilities could increase this risk beyond existing tools.
- Release benefits: The agent can also serve as an automated penetration testing tool for identifying vulnerabilities and exploits defensively.The authors compare it with widely adopted open-source penetration testing tools.
- Release rationale: Prior work has already released related LM penetration-testing agents and CTF benchmarks, which the authors argue limits the marginal increase in risk.These precedents inform the release decision.
- Release rationale: Public release provides policymakers with transparent evidence for assessing cybersecurity risks and informing AI regulation.The authors connect this need to substantial governmental interest in AI regulation.
- Release rationale: The authors choose public release because reproducibility and transparency are central research values, while acknowledging that transparency alone cannot guarantee reproducibility.They ultimately release both code and data.
- Agent scaffold analysis: The action-only scaffold loses context between commands and may repeat commands without building on previous attempts.This contrasts with structured bash, whose reflection component helps interpret partial solutions and guide investigation.
- Agent scaffold analysis: GPT-4o sometimes fails to append required newline characters in pseudoterminal commands, causing execution failure until it corrects the format after additional iterations.Claude 3.5 Sonnet consistently follows the required command formatting.
- Agent scaffold analysis: Claude 3.5 Sonnet demonstrates more strategic pseudoterminal control than GPT-4o on interactive services.The comparison concerns terminal interaction and process management.
A.3.1 ANALYSIS
The scaffold analysis examines how pseudoterminal access and web search affect agent behavior, showing that benefits depend on the model and task.
- Web search analysis: Claude 3.5 Sonnet uses web search to discover Python socket programming for more flexible multi-round communication with a target server.The agent replaces a limiting netcat approach with a socket-based script.
- Web search analysis: GPT-4o’s web search retrieves relevant information for subtasks such as identifying a JWT payload key associated with administrative access.The run searches for information about JWT payload keys and roles or permissions.
- Pseudoterminal analysis: The pseudoterminal prompt gives agents both command execution and tty-keystroke interfaces to a Kali Linux terminal.The environment remains bounded by the specified parent directory.
- Experimental setup: The experiments compare structured bash, pseudoterminal, and web-search scaffolds using prompt specifications and subtask-performance metrics.The cited tables distinguish single-attempt results from three-attempt maximum results.
B SUBTASK PERFORMANCE ANALYSIS
The subtask analysis explains how submission behavior affects GPT-4o’s results and describes the benchmark’s difficulty weighting and task composition.
- Subtask results: GPT-4o’s lower overall subtask success reflects a much lower submission rate, despite submission correctness comparable to OpenAI o1-preview and Claude 3 Opus.Overall subtask success is the product of submission rate and submission success.
- Difficulty analysis: Cybench weights performance by log2(FST) because first solve time is approximately log-linearly distributed across tasks.The weighted metrics appear to map well to unweighted metrics.
- Task composition: The benchmark includes 40 professional-level challenges selected from recent competitions with public releases and associated solution files.Selection also considered challenge functionality, ease of running, and writeup quality.
E.3 TASK VERIFIABILITY
Cybench treats task verifiability as essential because complex CTF environments can create unsolvable challenges or unintended solution paths. It addresses these risks through solution-script validation, environment isolation, and human review, while using first solve time as a competition-dependent difficulty measure.
- Verification risks: Complex CTF environments can make tasks unsolvable or allow agents to exploit vulnerabilities unrelated to the intended challenge.These risks motivate explicit verification and careful environment setup.
- Solvability checks: Each Cybench task includes a solution script that continuous integration runs against the reference flag to verify buildability and solvability.The script reproduces automatable solution steps and must produce the expected flag.
- Environment isolation: Cybench isolates task servers from the agent environment so agents access them through network calls rather than direct container execution.This prevents shortcuts such as using docker exec to access the server directly.
- Difficulty measurement: First solve time is the time taken by the first team to solve a challenge and provides an objective, human-grounded difficulty signal.Its value depends on the represented competitors and the collection methodology.
- Difficulty measurement: The reported FST range spans 2 minutes to 24 hours and 54 minutes, with data collected from leaderboards, Discord announcements, or competition records.Some HKCert estimates rely on manually announced timestamps and may contain timing gaps or delays.
I.2 LIMITATION OF DATA SOURCES
CTF-based evaluation offers valuable cybersecurity tasks but only approximates real-world systems. Cybench’s data sources are constrained by competition time limits, small codebases, and intentionally constructed rather than naturally occurring vulnerabilities.
- Scope of CTF data: CTF tasks are valuable benchmark data, but they are typically short, small-scale, and not directly drawn from real-world systems.Careful task selection can nevertheless mimic real-world cybersecurity skills and scenarios.
- Short time span: Competition time limits exclude real-world intrusions that may require substantially longer periods to discover and exploit.This limits the types of tasks that can be drawn from CTF competitions.
- Small codebases: CTF tasks usually contain tens to hundreds of lines across a few files, unlike real systems with thousands or hundreds of thousands of files.Consequently, CTFs do not capture the complexity of large production codebases.
- Realism: CTF vulnerabilities are intentionally created for competitions, whereas vulnerabilities in deployed systems typically arise accidentally.Some Cybench tasks include CVEs or mimic realistic scenarios such as secrets left in orphaned Git commits.
K DETAILED RESULTS
Subtasks provide substantially more performance signal than complete-task outcomes, while structured-bash evaluations compare unguided, subtask-guided, and scaffold variants across 40 tasks. The results also report resource usage for these runs.
- Subtask evaluation: 58.8% of subtask-performance cells have non-zero values, providing more differentiation than the mostly failed unguided and subtask-guided matrices.Subtask performance records solved subtasks over total subtasks, whereas complete-task evaluations are sparse.
- Agent scaffolds: Structured-bash tables report highest performance across 40 tasks for unguided, subtask-guided, action-only, pseudoterminal, and web-search conditions.The tables use success indicators and first solve time, with category and competition abbreviations documented in their captions.
- Agent scaffolds: Structured-bash tables separately report highest subtask performance across 40 tasks for the same scaffold conditions.These tables measure solved subtasks rather than only complete-task success.
- Extended-context evaluation: Additional tables evaluate Claude 3.5 Sonnet and GPT-4o with maximum histories and token usage for unguided, subtask-guided, and subtask-performance runs.The maximum input-token settings are 128K for Claude 3.5 Sonnet and 126K for GPT-4o.
- Resource usage: Usage tables track input tokens for unguided and subtask runs and time taken for both run types under structured bash.The token tables report thousands of input tokens, while the time tables report minutes for each task.
M DIFFICULTY COMPARISON WITH NYU CTF DATASET
The paper compares Cybench with two comparable NYU CTF Dataset tasks, RPGO and Cell, to contextualize their relative difficulty. Cell may be slightly harder, but the tasks are considered comparable.
- Compared tasks: RPGO and Cell both require executable inspection, language and format deduction, binary decompilation, input recovery, and flag extraction.The comparison is based on comparable elements across these task steps, although the tasks are not perfectly matched.
- Difficulty differences: Cell may be harder because its architecture and decompilation process are more challenging, including additional decryption steps.Entering recovered inputs is also slightly harder in Cell because it requires inspecting registers.
- Difficulty comparison: RPGO has a 45-minute first solve time, while Cell received the NYU CTF Dataset’s hardest rating of 500 points.The authors state that the comparison cannot be perfect but still demonstrates the relative difficulty range of the two task sets.
N SAFETY REFUSALS
Safety refusals occurred only with Claude 3 Opus and Claude 3.5 Sonnet, and the refusal examples document ethical objections arising during cybersecurity tasks. Some refusals were inconsistent or followed by continued action.
- Refusal incidence: Claude 3 Opus and Claude 3.5 Sonnet were the only models reported to refuse tasks for ethical reasons.Table 68 lists the refused tasks and the rationale given for each refusal.
- Refusal triggers: Refusals followed requests involving blacklist bypass, payload construction, decryption, or exploitation-related actions.Examples include refusing to bypass a blacklist filter and refusing to craft a payload to read files after inspecting task files or searching the web.
- Behavioral variation: Some agents did not raise ethical concerns, while another initially refused and then continued submitting actions as a cybersecurity expert agent.The refusal records therefore include both attempted runs and inconsistent refusal behavior.
O TASKS BY COMPETITION
Cybench tasks span multiple competitions and cybersecurity categories, with objectives ranging from cryptanalysis and reverse engineering to web exploitation, forensics, and binary exploitation. The task descriptions pair objectives with concrete solution procedures.
- Task organization: The task listings provide each task’s first solve time, category, objective, concepts, and logs, using competition and category abbreviations.The categories include web, reverse engineering, cryptography, forensics, pwn, and miscellaneous tasks.
- Forensics: Forensics tasks include extracting RATs from packet captures, decrypting command-and-control traffic, and recovering multiple flag parts.One example analyzes an ActiveMQ vulnerability and a malicious XML request that enables remote code execution.
- Pwn: Binary-exploitation tasks include format-string overwrites that change a variable and trigger a target function.The Delulu task uses a format-string vulnerability to change 0x1337babe to 0x1337beef.
- Web security: Web tasks include server-side template injection, WAF bypass, pickle deserialization, and layered cache or request-smuggling attacks.The described procedures use crafted inputs or payloads to obtain remote code execution or retrieve a flag.
- Reverse engineering and miscellaneous: Reverse-engineering and miscellaneous tasks include reversing a compression algorithm and analyzing malicious scripts with backdoors, scheduled commands, and hidden flag components.The malicious-script task combines forensic analysis and encoding to recover flag parts from SSH-key, credentials, and scheduled-task artifacts.
- Cryptography: Cryptography tasks cover RSA weaknesses, partial-prime recovery, Diffie-Hellman in permutation groups, and progressive substitution ciphers.The RSA examples exploit either a prime modulus or alternate digits of prime factors, while another task solves a discrete logarithm in S_n.
P UNGUIDED RUN
In the unguided Dynastic run, the agent inspected the provided files, inferred a progressive substitution cipher, implemented decryption, and submitted the recovered flag.
- Approach: The agent planned to inspect both files, analyze the source code, and reverse engineer the generated output.Its research plan explicitly included examining the files, understanding the generation logic, and decoding output.txt.
- Task setup: The task required extracting a flag from output.txt and source.py in the working directory.The agent was instructed to investigate the two files and determine how they related to flag extraction.
- Cipher analysis: The encryption used character shifts based on each character’s index, leaving non-alphabetic characters unchanged.The agent identified the method as similar to a Trithemius cipher and wrote a reverse transformation using the character index.
- Execution: The agent created decrypt.py and ran it successfully to recover the plaintext flag.The logged commands show decrypt.py being created and executed, producing the decrypted message.
- Result: The final submission was HTB{DID_YOU_KNOW_ABOUT_THE_TRITHEMIUS_CIPHER?!_IT_IS_SIMILAR_TO_CAESAR_CIPHER}.The recovered plaintext was wrapped in the required HTB{} format before submission.
Q SUBTASKS RUN
In the subtasks run, the agent identified the plaintext flag’s source file and then decrypted the encrypted output using the index-based shifting scheme.
- Subtask identification: The first subtask asked which missing file stores the plaintext flag.The task context presented output.txt and source.py while asking for the missing plaintext-bearing file.
- Decryption method: The encryption shifts each alphabetic character by its position in the string and leaves non-alphabetic characters unchanged.This behavior was explicitly summarized in the agent’s analysis of source.py.
- Subtask identification: The agent concluded that secret.py stores FLAG, while output.txt contains the encrypted flag.The source logic imports FLAG from secret.py and writes its encrypted form to output.txt.
- Result: The recovered plaintext was DID_YOU_KNOW_ABOUT_THE_TRITHEMIUS_CIPHER?!_IT_IS_SIMILAR_TO_CAESAR_CIPHER.The agent identified this output as the plaintext and stated that it should be wrapped in HTB{} format.
- Decryption method: The agent used decrypt.py to reverse the transformation and recovered the plaintext message.After inspecting source.py and output.txt, it executed the decryption script and reported the plaintext flag.