What is deserialization?

A guide to testing insecure deserialization, where an application turns stored or received data back into objects. It covers Java, PHP, Python, .NET, and Ruby, including gadget chains—linked code paths that may make unsafe data execute actions.

Use it to test serialization and deserialization handling across supported programming languages.

It helps reveal when untrusted serialized data can cause unintended code or actions to run.

deserialization — Skill for Claude Code by mohdhaji87

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 mohdhaji87/payloadsallthethings-skills --skill deserialization

Clone the repo

git clone --depth 1 https://github.com/mohdhaji87/payloadsallthethings-skills

Made for: Claude Code.

Or install payloadsallthethings, the plugin that ships this one along with the rest of its 61 skills.

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/mohdhaji87/payloadsallthethings-skills/deserialization/github.svg)](https://agentmods.dev/skills/mohdhaji87/payloadsallthethings-skills/deserialization)

Your own site

<a href="https://agentmods.dev/skills/mohdhaji87/payloadsallthethings-skills/deserialization"><img src="https://agentmods.dev/badge/skills/mohdhaji87/payloadsallthethings-skills/deserialization/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/mohdhaji87/payloadsallthethings-skills/deserialization"><img src="https://agentmods.dev/badge/skills/mohdhaji87/payloadsallthethings-skills/deserialization.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 27 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,802 The whole file, excluding the scripts and references it only reads on demand.

Security scan B 2 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin unknown 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.

Model	Per session	Once invoked
Fable 5.1	$0.00027	$0.01802
Opus 5.5	$0.00011	$0.00721
Sonnet 5.5	$0.00005	$0.00360
Haiku 4.5	$0.00003	$0.00180

Measured 2mo ago against content hash ef1535f8a0b1, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade B, and why

deserialization scanned grade B 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 2mo 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.

Unrestricted tool accessmediumExcessive agency

A wildcard tool grant or "run any command" leaves no least-privilege boundary at all.

Serialization converts objects into a format for storage or transmission; deserialization reconstructs objects from that format. Insecure deserialization occurs when untrusted data is used to abuse application logic, den

Runs shell commandslowCapability

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

return (os.system, ('id',))

payloadsallthethings/skills/deserialization/SKILL.md · 304 lines

The source is not reproduced here

A licence we could not identify

The repository carries a LICENSE file, but it is custom or dual enough that GitHub cannot name it and neither can this catalogue. Unknown terms are not permission, so the body is not copied here. Read the licence at the source and decide for yourself.

Read it on GitHub

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.

2mo ago First seen · 304 lines · 27 tokens per session scan B ef1535f8a0b1

Subscribe to this mod's changes

deserialization is a skill published in the GitHub repository mohdhaji87/payloadsallthethings-skills (21 stars, last pushed 10mo ago), with no licence file. It adds 27 tokens to every session and 1,802 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it B with 2 findings (unrestricted tool access, runs shell commands). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.