fix(security): strengthen DOM-clobbering defenses - #199
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Expanded RESERVED_IDS with the many missing high-value clobbering targets (attributes, nodeName, getElementById, defaultView, implementation, DOM traversal props, document methods, …) and added duplicate-id stripping in sanitize-core: two elements sharing an id turn getElementById/named access into a clobberable HTMLCollection (the classic <a id=x><a id=x name=y> vector), so later duplicates are now dropped. Documented that the id/name denylist is defense-in-depth, not a complete guarantee — fully untrusted content should drop id/name entirely. Fixes #179 Co-Authored-By: Claude Fable 5 <[email protected]>
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Summary
Fixes #179 (Low; defense-in-depth).
DOM-clobbering protection only stripped
id/namevalues whose exact value was in a ~30-entry reserved list, and the classic duplicate-id HTMLCollection vector (<a id=x></a><a id=x name=y>) passed unchanged. The list was also missing many high-value targets (attributes,nodeName,getElementById,defaultView,implementation, …).Fix
RESERVED_IDSwith the missing global/document/node/traversal targets.sanitize-core.ts: the first occurrence of an id is kept; later elements sharing it have theiriddropped, so named access resolves to a single node.id/namedenylist is defense-in-depth, not a complete guarantee — fully untrusted content should dropid/nameentirely.Verification
id="x"reduced to one occurrence; several newly-added reserved ids (attributes,getElementById,defaultView,implementation) are stripped. Both fail on the pre-fix code.tsc --noEmitclean.🤖 Generated with Claude Code