CVE-2026-109778: Privilege escalation in the WebExtensions component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.

PriorityP349high8.8CVSS 3.1

AVNACLPRNUIRSUCHIHAH

EPSS

0.28%

19.1th percentile

Privilege escalation in the WebExtensions component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.

Affected

4 ranges

Vendor	Product	Version range	Fixed in
mozilla	firefox	< Firefox 158	Firefox 158
mozilla	firefox_esr	< Firefox ESR 153.5	Firefox ESR 153.5
mozilla	thunderbird	< Thunderbird 153.5	Thunderbird 153.5
mozilla	thunderbird	< Thunderbird 158	Thunderbird 158

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