CVE-2020-13965: Addressing XSS Vulnerability in Roundcube Webmail

A notable security vulnerability identified as CVE-2020-13965 has raised concerns among Roundcube Webmail users, affecting versions prior to 1.3.12 and 1.4.x before 1.4.5.

This vulnerability, involving a cross-site scripting (XSS) issue via malicious XML attachments, highlights the ongoing challenges in securing web applications.

In this article, we dive into the details of CVE-2020-13965, its implications, and the necessary steps for mitigation.

Overview of CVE-2020-13965

CVE-2020-13965 is an XSS vulnerability that arises when Roundcube Webmail processes XML attachments. The vulnerability is due to insufficient sanitization of XML data, which can be exploited to execute arbitrary HTML and script code in a user’s browser session in the context of the affected site.

Technical Details of CVE-2020-13965

The vulnerability has a CVSS 3.1 base score of 6.1 (MEDIUM), indicating a significant risk that warrants attention. The vector string reflects the exploitability via network (AV:N), low attack complexity (AC:L), no required privileges (PR:N), and a requirement for user interaction (UI:R).

Root Cause

The core issue stems from allowing ‘text/xml’ as a permissible type for preview, without adequate filtering or encoding to prevent the execution of embedded scripts.

Potential Impact

Successful exploitation of this vulnerability could lead to:

#1 Unauthorized actions performed on behalf of the user, potentially leading to data theft or manipulation.

#2 Compromised user sessions, particularly in environments where multiple users access Roundcube Webmail.

Mitigation Strategies

Roundcube has addressed this vulnerability by releasing updates in versions 1.3.12 and 1.4.5, which include necessary patches to remediate the issue. Users are urged to:

Update Immediately: Upgrade to the latest versions of Roundcube Webmail as specified in the release notes.

Review Security Settings: Ensure that content security policies are strictly defined to mitigate the impact of potential XSS vulnerabilities.

    Alternative Actions

    For environments where updates cannot be applied immediately:

    Content Filtering: Implement additional content filtering on the server side to sanitize XML and other input types that may contain executable code.

    User Education: Educate users about the risks of opening attachments from unknown or untrusted sources.

      Best Practices for Webmail Security

      Maintain regular updates of all web applications, including webmail solutions like Roundcube, to protect against known vulnerabilities.

      Enhanced Input Sanitization

      Apply robust input validation and sanitization techniques to prevent XSS and other types of injection attacks.

      Security Awareness

      Promote security awareness among users, emphasizing safe practices such as recognizing phishing attempts and handling email attachments with caution.


      The CVE-2020-13965 vulnerability in Roundcube Webmail serves as a reminder of the critical need for comprehensive security measures in web-based email platforms. By understanding the vulnerability and implementing suggested mitigations, organizations can significantly reduce the risk of exploitation and safeguard their information assets.

      For more insights and proactive cybersecurity solutions, connect with Datacipher. Our team is dedicated to providing expert advice and services to strengthen your security posture and counter evolving cyber threats.

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