auditing-presigned-url-scope-abuse SKILL.md skillA
auditing-presigned-url-scope-abuse 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/auditing-presigned-url-scope-abuse@git:20260827.b5f41a4Pins git:20260827.b5f41a4 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/auditing-presigned-url-scope-abuse/SKILL.md- Versions recorded
- 1
- Latest version
- git:20260827.b5f41a4, committed Aug 27, 2026
- Size
- 9,108 bytes
- Repository stars
- 26
- License
- MIT
Audit presigned object-storage URLs for scope that grants more than the request intended: a signature that covers a broader key, prefix, or bucket than the user should reach, an overlong expiry, a method or content-type left unconstrained, or a signer identity whose permissions exceed the caller's. Covers presigned GET and PUT URLs for S3 and compatible stores, where the signed policy is the only boundary once the URL leaves the server, and where an attacker who edits the key, reuses the URL…
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
# Auditing presigned URL scope abuse: when the signature grants more than the request A presigned URL turns a server-side permission into a standalone credential: once minted, it grants whatever the signature covers to anyone holding the URL, with no further authorization check at the store. That is convenient and precisely why it leaks. If the service signs a key the caller supplied without confirming the caller owns it, the URL reads or writes another user's object. If the signed policy leaves the key prefix, the HTTP method, the content type, or the expiry looser than the request needed, the holder does more than intended: reads a sibling object, overwrites a path they were only meant to read, or replays the URL long after it should have died. The signer's own identity matters too, because the URL inherits its permissions, not the caller's. You audit these by comparing the signed scope against the caller's actual entitlement. ## When to use - A service mints presigned object-storage URLs so clients read or write a store directly. - The object key, prefix, bucket, or upload parameters in a presign request come from the caller. …
Read the whole file at its exact version.
How to install
mdr add unboundcompute/security-agent-skills/auditing-presigned-url-scope-abuse@sha256:c41e3ab3b292bfccThe line at the top of this page pins the label git:20260827.b5f41a4, 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_b2kij6d334sfe3u4)
2 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 1 version of this file, committed on Aug 27, 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 (9108 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_b2kij6d334sfe3u4 GET https://markdownregistry.com/api/v1/resolve?ref=unboundcompute/security-agent-skills/auditing-presigned-url-scope-abuse GET https://markdownregistry.com/api/v1/blob/c41e3ab3b292bfcca4b4c13dae4ef56766136b797611bf6dc4dafbc01b23e317
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.