Same-Origin Policy Bypass in Firefox Extension with Cross-Origin Favicon Reference

CVE-2021-23986 · MEDIUM Severity

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

A malicious extension with the 'search' permission could have installed a new search engine whose favicon referenced a cross-origin URL. The response to this cross-origin request could have been read by the extension, allowing a same-origin policy bypass by the extension, which should not have cross-origin permissions. This cross-origin request was made without cookies, so the sensitive information disclosed by the violation was limited to local-network resources or resources that perform IP-based authentication. This vulnerability affects Firefox < 87.

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