CVE-2017-5421: Mozilla Firefox

High severity, CVSS 7.5. EPSS: 1.9% chance of exploitation in the next 30 days.

A malicious site could spoof the contents of the print preview window if popup windows are enabled, resulting in user confusion of what site is currently loaded. This vulnerability affects Firefox < 52 and Thunderbird < 52.

Affected products

• Mozilla Firefox: before 52.0. (fixed in 52.0.)
• Mozilla Thunderbird: before 52.0. (fixed in 52.0.)

Published 2018-06-11. Last modified 2026-06-17.