fix: reject path traversal in alias extras and validate redirect location - #645
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…tion Extras containing parent directory references (..), backslashes, or encoded path separators are rejected before the alias redirect is constructed. A secondary check ensures the constructed location does not resolve to a protocol-relative or absolute URL outside the expected origin.
wkillerud
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Aug 21, 2026
validators.extra() from @eik/common now performs this validation. The handler retains only the defence-in-depth location check that ensures the constructed redirect stays within the expected origin.
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The @eik/common package needs to be published before this one can pass test vise. |
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## [2.2.2](v2.2.1...v2.2.2) (2026-08-21) ### Bug Fixes * reject path traversal in alias extras and validate redirect location ([#645](#645)) ([be1a9ef](be1a9ef))
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🎉 This PR is included in version 2.2.2 🎉 The release is available on: Your semantic-release bot 📦🚀 |
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Extras containing path traversal sequences are rejected before the alias redirect is constructed. A secondary check ensures the constructed redirect location does not resolve outside the expected origin.
The problem
A request such as:
After one round of percent-decoding (performed by the handler), the extras become:
path.jointreats%2Fand%5Cas opaque literals, so no traversal happens at the application level. However, when the redirectLocationheader is followed by an HTTP client that decodes percent-encoding, the path resolves through the..segments and%5C(backslash) becomes/, producing a protocol-relative URL (//external.example) that points to an external host.What this PR adds
Input validation —
validators.extra()from@eik/common(now non-trivial as of v5.2.1) rejects extras containing traversal sequences before the redirect is constructed.Location guard — after constructing the redirect location, a check asserts it does not start with
//or match an absolute URL scheme (https?://). This is defence-in-depth on the output, independent of input validation.What remains allowed
Normal extras are unaffected:
dist/style.css→ redirects to/pkg/@warp-ds/css/1.5.3/dist/style.cssmain/index.js→ redirects to/pkg/@warp-ds/css/1.5.3/main/index.jsCSS and JS relative references (e.g.
url('../fonts/font.woff2')) are also unaffected. Browsers resolve..client-side before making any HTTP request; the literal..never arrives at EIK.Tests
Tests are added that fail before the fix and pass after.