CVE-2021-21259 : Exploit Details and Defense Strategies

HedgeDoc is open source software that allows users to create real-time collaborative markdown notes. In HedgeDoc versions prior to 1.7.2, an attacker can inject arbitrary JavaScript into a note, which gets executed in slide mode. This vulnerability, known as Stored XSS, poses a high severity threat and has been assigned a CVSS base score of 7.4.

Understanding CVE-2021-21259

Stored XSS vulnerability in HedgeDoc slide mode.

What is CVE-2021-21259?

In HedgeDoc versions prior to 1.7.2, attackers can inject and execute arbitrary JavaScript in a note viewed in slide mode without needing authentication. Patched in version 1.7.2.

The Impact of CVE-2021-21259

This vulnerability allows attackers to execute malicious scripts within the context of HedgeDoc, potentially leading to data manipulation or other attacks.

Technical Details of CVE-2021-21259

Details of the vulnerability in HedgeDoc.

Vulnerability Description

Stored XSS allows attackers to inject JavaScript in HedgeDoc notes viewed in slide mode, with potential for data manipulation and other malicious activities.

Affected Systems and Versions

HedgeDoc versions before 1.7.2 are affected by this vulnerability.

Exploitation Mechanism

Attackers can inject malicious JavaScript into HedgeDoc notes, which gets executed when the note is viewed in slide mode.

Mitigation and Prevention

Preventive measures to address CVE-2021-21259 in HedgeDoc.

Immediate Steps to Take

Update HedgeDoc to version 1.7.2 or later to patch the vulnerability. Additionally, disallow loading JavaScript from 3rd party sites using the

Content-Security-Policy

header.

Long-Term Security Practices

Regularly update HedgeDoc to the latest version and implement security best practices to prevent future vulnerabilities.

Patching and Updates

Stay informed about security updates from HedgeDoc and apply patches promptly to ensure system security.