File downloads encoded with "blob:" and "data:" URL elements bypassed normal file download checks though the Phishing and Malware Protection feature and its block lists of suspicious sites and files. This would allow malicious sites to lure users into downloading executables that would otherwise be detected as suspicious. This vulnerability affects Firefox < 56, Firefox ESR < 52.4, and Thunderbird < 52.4.
Severity
CVSS 3.0
7.8 high
CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
EPSS
1.2% chance of exploitation in the next 30 days; higher than 67% of CVEs (scores of 2026-10-31)