CVE-2020-26870 : What You Need to Know

Cure53 DOMPurify before 2.0.17 allows mutation XSS due to a serialize-parse roundtrip issue that can change the namespace from HTML to MathML.

Understanding CVE-2020-26870

Cure53 DOMPurify before version 2.0.17 is vulnerable to mutation XSS, potentially leading to security risks.

What is CVE-2020-26870?

This CVE refers to a vulnerability in Cure53 DOMPurify before version 2.0.17 that enables mutation XSS by altering the namespace from HTML to MathML during a serialize-parse roundtrip.

The Impact of CVE-2020-26870

The vulnerability allows attackers to execute malicious code within the context of a website, posing a risk of unauthorized actions and data theft.

Technical Details of CVE-2020-26870

Cure53 DOMPurify before 2.0.17 is susceptible to mutation XSS due to improper handling of namespace changes.

Vulnerability Description

The issue arises from a serialize-parse roundtrip that may not return the original DOM tree, leading to a namespace switch from HTML to MathML, as demonstrated by nesting FORM elements.

Affected Systems and Versions

Product: Not applicable
Vendor: Not applicable
Versions affected: All versions before 2.0.17

Exploitation Mechanism

Attackers can exploit this vulnerability by manipulating the namespace during a serialize-parse roundtrip, allowing them to inject and execute malicious scripts.

Mitigation and Prevention

To address CVE-2020-26870, immediate actions and long-term security practices are essential.

Immediate Steps to Take

Update Cure53 DOMPurify to version 2.0.17 or newer to mitigate the vulnerability.
Implement input validation and output encoding to prevent XSS attacks.

Long-Term Security Practices

Regularly monitor security advisories and update software promptly.
Conduct security assessments and penetration testing to identify and remediate vulnerabilities.

Patching and Updates

Apply patches and updates provided by Cure53 to ensure the latest security fixes are in place.