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8.1 High

CVE-2026-100803 Same-origin policy bypass in the WebExtensions component

Description

Same-origin policy bypass in the WebExtensions component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.

Affected products and versions

Product Affected versions Fixed in
Firefox 157 earliest → < 157 157
Firefox 153.4 earliest → < 153.4 153.4
Firefox 140.17 earliest → < 140.17 140.17
Firefox 115.42 earliest → < 115.42 115.42
Thunderbird 157 earliest → < 157 157
Thunderbird 153.4 earliest → < 153.4 153.4
Thunderbird 140.17 earliest → < 140.17 140.17

Other CVEs of Firefox

The 2221 CVEs of Firefox →
CVE-2026-120572 Incorrect boundary conditions in the Layout: Block and Inline component 8.8 High CVE-2026-118027 Frame poisoning in the Layout component 9.1 Critical CVE-2026-118025 Other issue in the SVG component 8.8 High CVE-2026-118026 Invalid pointer in the JavaScript: GC component 8.8 High
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