A maliciously crafted page loaded to the sidebar through a bookmark can reference a privileged chrome window and engage in limited JavaScript operations violating cross-origin protections. This vulnerability affects Firefox < 50.
Severity
CVSS 3.0
8.0 high
CVSS:3.0/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
EPSS
1.9% chance of exploitation in the next 30 days; higher than 79% of CVEs (scores of 2026-10-31)