CVE-2026-57963

Chat UI manipulation by injection

State: Published
Severity: 6.5 Medium
Published: Jul 1, 2026
Updated: Jul 1, 2026
Reserved: Jun 26, 2026

Description

An attacker who can send HTML chat messages (via Matrix or XMPP) can inject arbitrary styled content, phishing links, and CSS that manipulates the chat UI. This vulnerability was fixed in Thunderbird 152.0.1 and Thunderbird 140.12.1.

Scores

CVSS	Score	Vector	Source
3.1	6.5 Medium	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N	CISA-ADP

Weaknesses

CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Affected Products

Product	Versions
ThunderbirdMozilla	140.12.1 through 140.*Not affected 152.0.1 and laterNot affected

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2042910
https://www.mozilla.org/security/advisories/mfsa2026-63/
https://www.mozilla.org/security/advisories/mfsa2026-64/

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