CVE-2018-5115: Canonical Ubuntu Linux

High severity, CVSS 7.5. EPSS: 2.5% chance of exploitation in the next 30 days.

If an HTTP authentication prompt is triggered by a background network request from a page or extension, it is displayed over the currently loaded foreground page. Although the prompt contains the real domain making the request, this can result in user confusion about the originating site of the authentication request and may cause users to mistakenly send private credential information to a third party site. This vulnerability affects Firefox < 58.

Affected products

• Canonical Ubuntu Linux: version 14.04 only; version 16.04 only; version 17.10 only
• Mozilla Firefox: up to and including 57.0.4

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