When entered directly, Reader Mode did not strip the username and password section of URLs displayed in the addressbar. This can be used for spoofing the domain of the current page. This vulnerability affects Firefox < 54.
Severity
CVSS 3.0
7.5 high
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
EPSS
1.9% chance of exploitation in the next 30 days; higher than 79% of CVEs (scores of 2026-10-31)