CVE-2025-58054

XSS in Discourse ≤ 3.5.0

XSS

Published

01 October 2025

Modified

23 October 2025

Patch / advisory

View advisory

CVSS Score v3.1 3.5

Click a component to see what it means

Raw vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:N

EPSS Score 0.0019 9th percentile

Risk Priority 30 floored blend · peak EPSS

Summary

CVE-2025-58054 is a low-severity Basic XSS (CWE-80) vulnerability in Discourse Discourse. Its CVSS base score is 3.5 (Low).

Operationally, exploitation aligns with the MITRE ATT&CK technique Content Injection (T1659); ranked at the 9th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-10 (Information Input Validation) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

EU & UK References

🇪🇺 ENISA EUVD: EUVD-2025-33227

Vulnerability Data

Discourse is an open-source community discussion platform. Versions 3.5.0 and below are vulnerable to XSS attacks through parsing and rendering of chat channel titles and chat thread titles via the quote message functionality when using the rich text editor. This…

issue is fixed in version 3.5.1.

CWE(s): CWE-80

Related Threats

MITRE ATT&CK Enterprise Techniques

T1659 Content Injection Initial Access

Adversaries may gain access and continuously communicate with victims by injecting malicious content into systems through online network traffic.

attack.mitre.org →

T1539 Steal Web Session Cookie Credential Access

An adversary may steal web application or service session cookies and use them to gain access to web applications or Internet services as an authenticated user without needing credentials.

attack.mitre.org →

T1189 Drive-by Compromise Initial Access

Adversaries may gain access to a system through a user visiting a website over the normal course of browsing.

attack.mitre.org →

Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-27166Same product: Discourse Discourse

CVE-2026-53963Same product: Discourse Discourse

CVE-2023-22454Same product: Discourse Discourse

CVE-2025-48954Same product: Discourse Discourse

CVE-2023-22468Same product: Discourse Discourse

CVE-2023-43659Same product: Discourse Discourse

CVE-2026-33411Same product: Discourse Discourse

CVE-2023-25172Same product: Discourse Discourse

CVE-2024-52794Same product: Discourse Discourse

CVE-2026-55424Same product: Discourse Discourse

Affected Assets

discourse

3.6.0 · ≤ 3.5.0 · ≤ 3.6.0

Mitigating Controls

Control response

Prevent

Stop it (NIST 800-53)

—

Detect

Catch it (NIST detect / respond)

—

Harden

Shrink the surface (DISA STIG)

—

Validate

Prove the fix (OWASP ASVS)

V1.2.1
V1.3.1
V1.3.3
V1.3.4

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation good match

Developer testing and evaluation can discover missing or incorrect neutralization of script tags through targeted XSS test cases.

SI-10 Information Input Validation good match

Input validation explicitly requires checking and neutralizing untrusted web inputs containing script-related characters before they reach a downstream renderer.

SA-8 Security and Privacy Engineering Principles partial match

Secure engineering principles include mandatory output encoding and neutralization of HTML metacharacters to stop injection at the source.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match

prevents

Secure SDLC practices directly require output encoding and input validation that prevent basic XSS.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match

finds

Security testing in development catches unneutralized script tags before release.

A.8.25 Secure development life cycle partial match

prevents

Secure SDLC mandates input validation and output encoding that directly prevent basic XSS.

A.8.26 Application security requirements partial match

prevents

Application security requirements explicitly call for neutralization of script-related HTML tags.

A.8.28 Secure coding partial match

prevents

Secure coding standards require proper escaping of <, >, & to block XSS.