CVE-2017-7839: Mozilla Firefox

Medium severity, CVSS 6.1. EPSS: 1.1% chance of exploitation in the next 30 days.

Control characters prepended before "javascript:" URLs pasted in the addressbar can cause the leading characters to be ignored and the pasted JavaScript to be executed instead of being blocked. This could be used in social engineering and self-cross-site-scripting (self-XSS) attacks where users are convinced to copy and paste text into the addressbar. This vulnerability affects Firefox < 57.

Affected products

• Mozilla Firefox: up to and including 56.0.2

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