Is CVE-2026-53963 actively exploited?

No active exploitation of CVE-2026-53963 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2026-53963 be exploited remotely?

Yes. CVE-2026-53963 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2026-53963?

CVE-2026-53963 has a CVSS score of 9.0 (CRITICAL).

HOME VULNERABILITIESCVE-2026-53963

CRITICAL

CVE-2026-53963

CWE-79Published: July 9, 2026· Updated: Jul 14, 2026

9.0

CVSS v3.1

EPSS:0.39%probability of exploitation in 30 daysPercentile:31.3th

Official Description

Discourse is an open-source discussion platform. Prior to 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5, a malicious second factor name on an attacker-controlled account was not escaped in the delete confirmation dialog, allowing stored cross-site scripting when an administrator impersonated that account. This issue is fixed in versions 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5.

NVD Source

Risk Analysis

This critical vulnerability in Discourse allows for stored cross-site scripting (XSS) due to improper escaping of a malicious second factor name. An attacker can inject scripts that execute when an administrator impersonates the attacker's account. With a CVSS score of 9.0, this can lead to high impact on confidentiality, integrity, and availability.

No public exploit is currently known for this vulnerability. While it requires user interaction (UI:R) and prior authentication (PR:L), it is remotely exploitable.

Recommended Action

Users should upgrade Discourse to versions 2026.6.0, 2026.5.1, 2026.4.2, or 2026.1.5 or later. Implement strict input validation and output encoding for all user-supplied data.

Generated by the CTIWATCH analysis pipeline from this CVE's metadata (CVSS, EPSS, KEV status, exploit intelligence). Verify against vendor advisories before acting.

Technical Analysis

CVE-2026-53963 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 9.0.

The vulnerability has a "Changed" scope, meaning successful exploitation can impact components beyond the vulnerable component itself — such as the host operating system or adjacent services.

From a weakness classification perspective (CWE-79): Cross-site scripting (XSS) vulnerabilities allow attackers to inject malicious scripts into web pages viewed by other users.