url-validation-security SKILL.md skillA
url-validation-security from patrickserrano/lacquer is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add patrickserrano/lacquer/url-validation-security@git:20260725.3f0d943Pins git:20260725.3f0d943 in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- patrickserrano/lacquer
- Path
profiles/ios/skills/url-validation-security/SKILL.md- Versions recorded
- 1
- Latest version
- git:20260725.3f0d943, committed Jul 25, 2026
- Size
- 2,124 bytes
- Repository stars
- 5
- License
- MIT
Use when validating a user-provided or externally-sourced URL before it reaches `AVPlayer`, `URLSession`, or a `WKWebView` — building a positive- allowlist URL validator, or reviewing existing networking/media code for missing URL validation.
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
# URL Validation Security Posture
Validate **every** user-provided URL through a positive-allowlist validator
before it reaches `AVPlayer`, `URLSession`, or a `WKWebView`. Validate at
**both** the manager and service boundaries (the duplication is intentional
defense-in-depth). Known limitation: homograph / IDN look-alike hosts are not
detected.
The validator parses once via `URLComponents` and asserts: http/https scheme
only, non-empty host, no userinfo (credentials), a UTF-8 **byte-length** cap,
and rejection of C0 controls / DEL / literal & percent-encoded null bytes. The
dangerous-scheme denylist is redundant belt-and-suspenders.
```swift
enum SecureURLValidator {
/// Returns true only when the URL satisfies every required property.
/// Known limitation: homograph / IDN look-alike hosts are not detected.
nonisolated static func validate(_ urlString: String) -> Bool {
guard !urlString.isEmpty else { return false }
guard urlString.utf8.count <= 2048 else { return false }
guard !urlString.unicodeScalars.contains(where: { $0.value < 0x20 || $0.value == 0x7F }) else { return false }
…Read the whole file at its exact version.
How to install
mdr add patrickserrano/lacquer/url-validation-security@sha256:f5025547c35c2ec4The line at the top of this page pins the label git:20260725.3f0d943, 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_l75tdhmk3szg5ntl)
4 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 1 version of this file, committed on Jul 25, 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 (2124 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
patrickserrano/lacquer · 5 stars · license MIT · pushed 2026-11-06 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_l75tdhmk3szg5ntl GET https://markdownregistry.com/api/v1/resolve?ref=patrickserrano/lacquer/url-validation-security GET https://markdownregistry.com/api/v1/blob/f5025547c35c2ec41d32d51e526b706147a023e3638412a7b6dc5d43c80a7e03
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.