CVE-2025-1018: Fullscreen notification is not displayed when fullscreen is re-requested

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-02-04 · updated 2026-10-05
Weakness: CWE-1021

Description

The fullscreen notification is prematurely hidden when fullscreen is re-requested quickly by the user. This could have been leveraged to perform a potential spoofing attack. This vulnerability was fixed in Firefox 135 and Thunderbird 135.

Affected products

Mozilla Firefox: before 135.0 — fixed in 135.0
Mozilla Thunderbird: from 131.0 before 135.0 — fixed in 135.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 135.0; Mozilla Thunderbird 135.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1910818
https://www.mozilla.org/security/advisories/mfsa2025-07/
https://www.mozilla.org/security/advisories/mfsa2025-11/

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