fix: invalidate sandboxed preload code cache when source changes without changing length#51930
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…out changing length V8's CachedData source check hashes only the source length, so a preload edit that preserves byte length consumed the stale blob and ran the old bytecode. Bind cache entries to sha256 of the source: the renderer ships the hash of what it compiled, the browser stores it in the cache entry and only serves a blob whose hash matches the contents it just read. Reject cache writes for preload ids not served to the sending frame.
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MarshallOfSound
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Jun 9, 2026
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I have automatically backported this PR to "43-x-y", please check out #51932 |
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I have automatically backported this PR to "42-x-y", please check out #51933 |
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Description
The sandboxed preload code cache (#51602) relied on V8's
CachedDatavalidation to reject stale blobs, but V8's source check hashes only the source length. Updating a preload without changing its byte length made renderers silently run the old version's bytecode.Cache entries are now bound to the sha256 of the preload source: the renderer ships the hash of what it compiled with the produced blob, and the browser only serves a blob whose recorded hash matches the contents it just read. The browser also rejects cache writes for preload ids not served to the sending frame. Old-format cache files read as a miss and self-heal.
Checklist
npm testpasses (preload code cache suite)Release Notes
Notes: Fixed sandboxed preload scripts running a stale cached version after the script was modified without its file size changing.