CVE-2026-4915 Server panic via outgoing webhook responses

Mattermost versions 11.6.x = 11.6.0, 11.5.x = 11.5.3, 11.4.x = 11.4.4, 10.11.x = 10.11.14 fail to filter nil elements from outgoing webhook attachment payloads before processing, which allows an authenticated user to cause a denial of service server process termination via a crafted webhook...

Trix has a stored XSS vulnerability through its attachment attribute

Impact The Trix editor, in versions prior to 2.1.16, is vulnerable to XSS attacks through attachment payloads. An attacker could inject malicious code into a data-trix-attachment attribute that, when rendered as HTML and clicked on, could execute arbitrary JavaScript code within the context of th...