CVE-2025-3523

User Interface (UI) Misrepresentation of attachment URL

CVSS 6.4 MEDIUMEPSS 0.3%CWE-451

When an email contains multiple attachments with external links via the X-Mozilla-External-Attachment-URL header, only the last link is shown when hovering over any attachment. Although the correct link is used on click, the misleading hover text could trick users into downloading content from untrusted sources. This vulnerability was fixed in Thunderbird 137.0.2 and Thunderbird 128.9.2.

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

Affected products

Mozilla · Thunderbird

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References

https://bugzilla.mozilla.org/show_bug.cgi?id=1958385 https://www.mozilla.org/security/advisories/mfsa2025-26/https://www.mozilla.org/security/advisories/mfsa2025-27/