CVE-2025-6430: Mozilla Firefox

Medium severity, CVSS 6.1. EPSS: 0.3% chance of exploitation in the next 30 days.

When a file download is specified via the `Content-Disposition` header, that directive would be ignored if the file was included via a `<embed>` or `<object>` tag, potentially making a website vulnerable to a cross-site scripting attack. This vulnerability was fixed in Firefox 140, Firefox ESR 128.12, Thunderbird 140, and Thunderbird 128.12.

Affected products

• Mozilla Firefox: before 128.12.0 (fixed in 128.12.0); before 140.0 (fixed in 140.0)

Published 2025-06-24. Last modified 2026-10-05.