CVE-2026-53899 is a vulnerability in Mozilla Firefox
Published on June 16, 2026
Cross-origin cookies could be leaked when opening a PDF link
Firefox for iOS used partial domain matching when attaching cookies to PDF requests, allowing a malicious site on a suffix domain to receive cookies belonging to the target site. This vulnerability was fixed in Firefox for iOS 152.0.
Products Associated with CVE-2026-53899
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Affected Versions
Mozilla Firefox for iOS:- Version 152.0, <= * is unaffected.