CVE-2020-15676 Explained : Impact and Mitigation

Firefox sometimes ran the onload handler for SVG elements that the DOM sanitizer decided to remove, resulting in JavaScript being executed after pasting attacker-controlled data into a contenteditable element. This vulnerability affects Firefox < 81, Thunderbird < 78.3, and Firefox ESR < 78.3.

Understanding CVE-2020-15676

This CVE-2020-15676 vulnerability impacts Firefox, Thunderbird, and Firefox ESR versions.

What is CVE-2020-15676?

CVE-2020-15676 is a security vulnerability that allows for XSS attacks when pasting attacker-controlled data into a contenteditable element in Firefox, Thunderbird, and Firefox ESR.

The Impact of CVE-2020-15676

The vulnerability could lead to the execution of malicious JavaScript code when pasting manipulated data into a contenteditable element, potentially compromising user data and system integrity.

Technical Details of CVE-2020-15676

This section provides more in-depth technical insights into the CVE-2020-15676 vulnerability.

Vulnerability Description

The issue arises from Firefox running the onload handler for SVG elements that the DOM sanitizer removes, enabling the execution of JavaScript after pasting attacker-controlled data into a contenteditable element.

Affected Systems and Versions

Firefox < 81
Thunderbird < 78.3
Firefox ESR < 78.3

Exploitation Mechanism

Attackers can exploit this vulnerability by inserting malicious JavaScript code into a contenteditable element, triggering its execution upon pasting manipulated data.

Mitigation and Prevention

To safeguard systems from CVE-2020-15676, follow these mitigation strategies:

Immediate Steps to Take

Update Firefox, Thunderbird, and Firefox ESR to versions 81, 78.3, and 78.3 respectively.
Avoid pasting data from untrusted sources into contenteditable elements.

Long-Term Security Practices

Regularly update browsers and email clients to the latest versions.
Educate users on safe browsing practices and the risks associated with pasting data from unknown sources.

Patching and Updates

Stay informed about security advisories and promptly apply patches released by Mozilla to address known vulnerabilities.