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CVE-2026-3471

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

MEDIUM
6.5
CVSS Score
Published: May 18, 2026 at 08:45 AM UTC
Updated: June 17, 2026 at 10:43 AM UTC
2 products affected across 1 vendorMattermost DesktopMattermost

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Severity
MEDIUM6.5
Exploit prediction
EPSS 0.2%
SSVC
No known exploit

Description

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

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Mattermost Desktop· Mattermost
95%
v ≤ 5.4.13.06.0.0 ≤ v ≤ 6.0.16.1.0 ≤ v < 6.2.0
Affected range stops below 6.2.0, so it looks safe — our inference, not a vendor statement
Mattermost· Mattermost
60%
v ≤ 5.4.13v ≤ 6.0.1
Vendor states this is fixed in 5.13.5.0 (unaffected)
Vendor states this is fixed in 6.1.1.0 (unaffected)
Vendor states this is fixed in 6.2.0 (unaffected)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (1)

Vendor Advisory
Source: cverecord
https://mattermost.com/security-updates

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

6.5MEDIUMMattermost
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusANALYZED
CWE
CWE-939

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