CVE-2026-57963: Chat UI manipulation by injection

Published Jun 30, 2026
·
Updated

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.

Affected Software

5 affected componentsFixes available
Mozilla Thunderbird<152.0.1, <140.12.1
Mozilla Thunderbird<140.12.1
140.12.1
Mozilla Thunderbird<152.0.1
152.0.1
Mozilla Thunderbird<140.12.1
Mozilla Thunderbird<152.0.1

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 140.12.1
  2. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 152.0.1
  3. Upgrade

    Upgrade Mozilla Thunderbird to a version that resolves this vulnerability.

    Fixed in 152.0.1
  4. Upgrade

    Upgrade Mozilla Thunderbird to a version that resolves this vulnerability.

    Fixed in 140.12.1

Event History

Jun 30, 2026
CVE Published
via Mozilla·12:00 AM
Data Sourced
via Mozilla·12:00 AM
DescriptionSeverityAffected Software
Updated
via Mozilla·12:00 AM
Affected Software
Jul 1, 2026
CVE Published
via MITRE·12:58 AM
Data Sourced
via MITRE·12:58 AM
Description
Data Sourced
via NVD·02:17 AM
DescriptionSeverityWeaknessAffected Software

Parent advisories

This vulnerability appears in the following advisories.

Peer vulnerabilities

Found alongside the following vulnerabilities.

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Frequently Asked Questions

1

What is the severity of CVE-2026-57963?

The severity of CVE-2026-57963 is rated as medium with a CVSS score of 6.5.

2

What type of vulnerability is CVE-2026-57963?

CVE-2026-57963 is a Cross-Site Scripting (XSS) vulnerability that allows HTML chat message injection.

3

How does CVE-2026-57963 impact Mozilla Thunderbird users?

CVE-2026-57963 allows attackers to manipulate the chat UI, potentially leading to phishing or misleading content.

4

How do I fix CVE-2026-57963 in Mozilla Thunderbird?

To fix CVE-2026-57963, ensure you update to the latest version of Mozilla Thunderbird that addresses this vulnerability.

5

What can attackers achieve with CVE-2026-57963?

Attackers can use CVE-2026-57963 to inject arbitrary styled content and phishing links into chat messages.

Company

Resources

Contact

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