Medium (5.4). EPSS 1.4% chance of exploitation in the next 30 days.
The content security policy (CSP) "sandbox" directive did not create a unique origin for the document, causing it to behave as if the "allow-same-origin" keyword were always specified. This could allow a Cross-Site Scripting (XSS) attack to be launched from unsafe content. This vulnerability affects Firefox < 56, Firefox ESR < 52.4, and Thunderbird < 52.4.
Severity
CVSS 3.0
5.4 medium
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
EPSS
1.4% chance of exploitation in the next 30 days; higher than 73% of CVEs (scores of 2026-10-31)