CVE-2026-92074: Mitigation bypass in the Popup Blocker component

Severity: high (CVSS 8.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-15 · updated 2026-10-05
Weakness: CWE-693

Description

Mitigation bypass in the Popup Blocker component. This vulnerability was fixed in Firefox 156, Firefox ESR 153.3, Thunderbird 156, and Thunderbird 153.3.

Affected products

Mozilla Firefox: before 153.3.0; from 154.0.0 before 156.0.0 — fixed in 153.3.0, 156.0.0
Mozilla Thunderbird: before 153.3.0; from 154.0 before 156.0 — fixed in 153.3.0, 156.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 153.3.0, 156.0.0; Mozilla Thunderbird 153.3.0, 156.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2063539
https://www.mozilla.org/security/advisories/mfsa2026-90/
https://www.mozilla.org/security/advisories/mfsa2026-93/
https://www.mozilla.org/security/advisories/mfsa2026-94/
https://www.mozilla.org/security/advisories/mfsa2026-96/

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