Description
The exception page for the HTTPS-Only feature, displayed when a website is opened via HTTP, lacked an anti-clickjacking delay, potentially allowing an attacker to trick a user into granting an exception and loading a webpage over HTTP. This vulnerability was fixed in Firefox 140 and Thunderbird 140.
Affected products
mozilla: firefox
References3
- www.mozilla.org/security/advisories/mfsa2025-51/ Vendor Advisory
- bugzilla.mozilla.org/show_bug.cgi?id=1955182 Permissions Required
- www.mozilla.org/security/advisories/mfsa2025-54/
Metrics
- CVSS 3.1
-
4.3
MEDIUM
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N - EPSS — exploit probability
- 0% percentile: 21 · as of 7 November 2026
- CWE
- CWE-1021
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