Individual skill

web-dom-clobbering

Overwrite a page's JavaScript variables using only injected HTML — no script needed. Load when a sanitizer allows tags/attributes but strips script, and the app reads config/state from the DOM or globals. Signals: HTML injection behind DOMPurify/an allowlist, client code using `window.X`, `document.getElementById(...)`, or `config.*` that could come from named elements.

skills/web/web-dom-clobbering/SKILL.md

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Last checked: Nov 7, 2026

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Repository stars (not skill ratings): 27
Repository last updated: Oct 14, 2026
License: MIT

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# DOM clobbering

## When it applies
You can inject HTML but not script (a sanitizer blocks JS), and the application's own JavaScript
reads values from named DOM elements or global properties. Clobbering turns pure markup into
control over those values — often the missing link to XSS or a logic bypass.

## Why it works
The browser auto-creates properties from element `id`/`name`: `<a id=x>` makes `window.x` (and
`document.x`) reference that element. Legacy code that does `var cfg = window.config || {}` or
`document.getElementById('token')` can be *clobbered* — you supply the element, so you control what
that "variable" resolves to.

## Method