CVE-2020-15139 : Exploit Details and Defense Strategies

In MyBB before version 1.8.24, a DOM-based XSS vulnerability exists due to improper handling of custom MyCode (BBCode) in the visual editor. Attackers can exploit this weakness by directing victims to a page with a malicious MyCode message.

Understanding CVE-2020-15139

What is CVE-2020-15139?

In MyBB versions prior to 1.8.24, a vulnerability allows for DOM-based XSS attacks through crafted MyCode messages in the visual editor.

The Impact of CVE-2020-15139

The vulnerability has a CVSS base score of 8.8 (High severity) with a high impact on confidentiality, integrity, and availability.

Technical Details of CVE-2020-15139

Vulnerability Description

MyBB before 1.8.24 mishandles custom MyCode in the visual editor, leading to a DOM-based XSS risk.

Affected Systems and Versions

Product: MyBB
Vendor: MyBB
Versions Affected: < 1.8.24

Exploitation Mechanism

Attack Complexity: Low
Attack Vector: Network
Privileges Required: None
User Interaction: Required
Scope: Unchanged

Mitigation and Prevention

Immediate Steps to Take

Upgrade MyBB to version 1.8.24 to mitigate the vulnerability.
Update the version attribute in the

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template for non-default themes.

Long-Term Security Practices

Regularly update MyBB and associated components.
Educate users on safe browsing practices.
Implement content security policies.

Patching and Updates

Ensure all software components are up to date to prevent exploitation.