Content Security Policy combined with HTTP to HTTPS redirection can be used by malicious server to verify whether a known site is within a user's browser history. This vulnerability affects Firefox < 50.
Severity
CVSS 3.0
5.3 medium
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
EPSS
1.8% chance of exploitation in the next 30 days; higher than 79% of CVEs (scores of 2026-10-31)