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lsd-cat
requested changes
Aug 19, 2026
| ); | ||
| export function isSameOriginURL(target: string, base: string) { | ||
| const baseURL = new URL(base); | ||
| const targetURL = new URL(target, baseURL); |
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new URL can throw on malformed URLs, and I don't think we catch that anywhere. Without #178 I think that could result in a WEBCAT bypass?
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Great! I wonder if an alternative to #178 could be instead to lint for uncaught throws or errors in CI instead, I'm gonna investigate a bit! Thanks for the patch here :)
lsd-cat
approved these changes
Aug 19, 2026
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Fixes #220.
It's worth noting that the URL constructor used in this PR and Firefox's internal URL parsing for Location headers don't behave exactly the same way: specifically, the URL constructor strips ASCII whitespace throughout the URL, while Firefox's internal handling only trims whitespace from the start of the URL. That means a URL like
https\t://example.com/appears absolute to the URL constructor but actually triggers a relative redirect. This PR doesn't address that issue, because the failure mode is safe.