What is the CVSS score of CVE-2026-28405?

CVE-2026-28405 has a CVSS 3.1 base score of 8.0 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H. EPSS exploitation probability: 0.0%.

Which versions of Markus are affected by CVE-2026-28405?

MarkUs versions prior to 2.9.1 contain a vulnerability that allows attackers to inject malicious content through student assignment submissions, potentially compromising the accounts and data of…. A patch is available.

How to fix or mitigate CVE-2026-28405?

Within 24 hours: Identify all instances of MarkUs and their versions; notify affected stakeholders of the vulnerability. Within 7 days: Apply vendor patch to upgrade to version 2.9.1 or later across all production and staging environments. Within 30 days: Conduct security audit of submission content handling, review access logs for suspicious activity, and implement automated patching procedures for future releases.

Markus CVE-2026-28405

HIGH

Cross-site Scripting (XSS) (CWE-79)

2026-03-05 security-advisories@github.com

XSS Markus

8.0

CVSS 3.1 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

8.0 HIGH

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

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

Required

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Analysis Generated

Mar 12, 2026 - 22:06 vuln.today

Patch released

Mar 10, 2026 - 19:53 nvd

Patch available

CVE Published

Mar 05, 2026 - 21:16 nvd

HIGH 8.0

DescriptionGitHub Advisory

MarkUs is a web application for the submission and grading of student assignments. Prior to version 2.9.1, the courses/<:course_id>/assignments/<:assignment_id>/submissions/html_content route reads the contents of a student-submitted file and renders them without sanitization. This issue has been patched in version 2.9.1.

AnalysisAI

MarkUs prior to version 2.9.1 fails to sanitize user-submitted file contents in the HTML rendering endpoint, allowing authenticated users with UI interaction to inject malicious scripts that execute in other users' browsers. An attacker can exploit this reflected cross-site scripting vulnerability to steal session tokens, modify grades, or perform actions on behalf of affected students and instructors. The vulnerability has been patched in version 2.9.1.

Technical ContextAI

Classified as CWE-79 (Cross-site Scripting (XSS)). Affects Markus. MarkUs is a web application for the submission and grading of student assignments. Prior to version 2.9.1, the courses/<:course_id>/assignments/<:assignment_id>/submissions/html_content route reads the contents of a student-submitted file and renders them without sanitization. This issue has been patched in version 2.9.1.

RemediationAI

A vendor patch is available — apply it immediately. Fixed in version 2.9.1.. Implement output encoding and Content Security Policy headers. Restrict network access to the affected service where possible.