CVE-2026-86853: Mozilla Firefox Mobile

Medium severity, CVSS 4.3. EPSS: 0.3% chance of exploitation in the next 30 days.

A malicious webpage could repeatedly trigger external URL schemes, causing system prompts or external application launches. This could make Firefox for iOS temporarily unusable until the page is closed. This vulnerability was fixed in Firefox for iOS 155.1.

Affected products

• Mozilla Firefox Mobile: before 155.1 (fixed in 155.1)

Published 2026-09-08. Last modified 2026-10-05.