CVE-2026-100803EPSS p7.6%

CVE-2026-100803CVE-2026-100803

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.

Scoring

CVSS 8.1 ()
VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
EPSS0.19% probability of exploitation · percentile 7.6% · 2026-10-05T12:00:23Z
Last modified2026-10-01
Sourced from NVD + FIRST.org EPSS. Curated for EU compliance use cases by Adam Lundqvist, Founder at SQUR.