Vulnerability library
Security checkJuly 23, 2026

PostCSS: Arbitrary file read and information disclosure via attacker-controlled sourceMappingURL in CSS comments

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High severitynpmpostcss

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Description

PostCSS’s PreviousMap parses the /*# sourceMappingURL=PATH */ comment from any CSS string passed to process() and dereferences PATH against the local filesystem with no scheme, allowlist, or traversal check.

Recommendation

Update the postcss package to the latest compatible version. Followings are version details:

  • Affected version(s): <= 8.5.11
  • Patched version(s): 8.5.12

References

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See something that needs correcting? Let us knowUpdated July 23, 2026