CVE-2025-6430: firefox XSS — Fix

Description

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.

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CVSS v3.1 Score

6.1

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Weakness Type (CWE)

CWE-79 Cross-site Scripting (XSS)

Affected Products

Vendor	Product	Versions
mozilla	firefox	< 128.12.0
mozilla	firefox	< 140.0

References

Advisories & Patches

https://www.mozilla.org/security/advisories/mfsa2025-51/ https://www.mozilla.org/security/advisories/mfsa2025-53/

Other References

https://bugzilla.mozilla.org/show_bug.cgi?id=1971140 https://www.mozilla.org/security/advisories/mfsa2025-54/ https://www.mozilla.org/security/advisories/mfsa2025-55/ https://lists.debian.org/debian-lts-announce/2025/06/msg00029.html https://lists.debian.org/debian-lts-announce/2025/07/msg00002.html

Frequently Asked Questions

What is CVE-2025-6430? +

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. It has a CVSS v3.1 base score of 6.1 (MEDIUM).

How severe is CVE-2025-6430? +

CVE-2025-6430 has a CVSS v3.1 score of 6.1 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-6430? +

CVE-2025-6430 affects products from mozilla, specifically: firefox. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-6430? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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