CVE-2012-1961: Mozilla Firefox

Medium severity, CVSS 4.3. EPSS: 2.1% chance of exploitation in the next 30 days.

Mozilla Firefox 4.x through 13.0, Firefox ESR 10.x before 10.0.6, Thunderbird 5.0 through 13.0, Thunderbird ESR 10.x before 10.0.6, and SeaMonkey before 2.11 do not properly handle duplicate values in X-Frame-Options headers, which makes it easier for remote attackers to conduct clickjacking attacks via a FRAME element referencing a web site that produces these duplicate values.

Affected products

• Mozilla Firefox: version 4.0 only; version 4.0.1 only; version 5.0 only; version 5.0.1 only; version 6.0 only; version 6.0.1 only; …
• Mozilla Seamonkey: up to and including 2.10; version 1.0 only; version 1.0.1 only; version 1.0.2 only; version 1.0.3 only; version 1.0.4 only; …
• Mozilla Thunderbird: version 5.0 only; version 6.0 only; version 6.0.1 only; version 6.0.2 only; version 7.0 only; version 7.0.1 only; …
• Mozilla Thunderbird ESR: version 10.0 only; version 10.0.1 only; version 10.0.2 only; version 10.0.3 only; version 10.0.4 only; version 10.0.5 only

Published 2012-07-18. Last modified 2026-06-16.