CVE-2026-3471CWE-939

Opening a window with {{javascript:alert()}} as URL causes crash in the Mattermost Desktop App

Medium · published May 18, 2026

CVSS v3.1
6.5
EPSS
0%
Percentile
24.6
In the wild
Unconfirmed
What it is

Mattermost Desktop App versions <=6.1 6.0.1 5.4.13.0 fail to prevent an invalid URL from loading in a pop-up window in the Mattermost Desktop App which allows a malicious server owner to repeated crash the application via calling {{window.open('javascript:alert()');}}. Mattermost Advisory ID: MMSA-2026-00618

The record
Technical detail
CVSS v3.1
6.5 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
CVSS v4.0
Not supplied
EPSS
0.00328 · 24.6th percentile
Weakness
CWE-939 · Improper Authorization in Handler for Custom URL Scheme
Published
2026-05-18T08:45Z
EPSS history
Timeline
  • 18 MAY 08:45Z
    Opening a window with {{javascript:alert()}} as URL causes crash in the Mattermost Desktop App
    cvelistv5