hunting-server-side-prototype-pollution SKILL.md skillA
hunting-server-side-prototype-pollution from unboundcompute/security-agent-skills is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add unboundcompute/security-agent-skills/hunting-server-side-prototype-pollution@git:20260826.c45369bPins git:20260826.c45369b in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- unboundcompute/security-agent-skills
- Path
skills/hunting-server-side-prototype-pollution/SKILL.md- Versions recorded
- 1
- Latest version
- git:20260826.c45369b, committed Aug 26, 2026
- Size
- 9,487 bytes
- Repository stars
- 26
- License
- MIT
Hunt server-side prototype pollution in JavaScript and TypeScript backends where untrusted input sets a __proto__, constructor, or prototype key through a recursive merge, a deep clone, a path-based set, or a query or body parser, polluting Object.prototype so a later property read returns an attacker value. Covers the pollution primitive (the write that reaches the prototype) and the gadget (a downstream read of an unset property that changes control flow, a command, a template, or a query).…
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# Hunting server-side prototype pollution: when one request changes every object In JavaScript, every plain object inherits from `Object.prototype`, so writing to that shared prototype changes the default value of a property on every object in the process. Server-side prototype pollution happens when untrusted input carries a `__proto__`, `constructor`, or `prototype` key into a recursive merge, a deep clone, or a path-based set that follows the key down to the prototype. The write by itself is a primitive; the impact comes later, when some other code reads a property that was never set and now returns the attacker's injected default. That gadget read can flip an authorization flag, inject an argument into a spawned command, or change a template or query. You find it by locating the pollution primitives and then the gadget reads they enable. ## When to use - A Node.js or server-side TypeScript service merges, clones, or path-assigns untrusted structured input. - A parser or utility recurses into keys from a request body, query string, or JSON document. - Later code reads object properties that may be unset, where an injected default would change behavior. ## Scope check …
Read the whole file at its exact version.
How to install
mdr add unboundcompute/security-agent-skills/hunting-server-side-prototype-pollution@sha256:34001dd188bbcd0bThe line at the top of this page pins the label git:20260826.c45369b, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_s7eamn36klaoy4gk)
2 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 1 version of this file, committed on Aug 26, 2026.
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (9487 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
unboundcompute/security-agent-skills · 26 stars · license MIT · pushed 2026-09-08 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_s7eamn36klaoy4gk GET https://markdownregistry.com/api/v1/resolve?ref=unboundcompute/security-agent-skills/hunting-server-side-prototype-pollution GET https://markdownregistry.com/api/v1/blob/34001dd188bbcd0b43ac6e04d143c9ebca0925beca5aed4d0f5c520421d452d8
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.