Zero-Day XSS Flaw Found in Roundcube Webmail Software

The Download

Security researchers have identified a zero-day cross-site scripting (XSS) vulnerability in Roundcube Webmail, one of the most widely deployed open-source webmail solutions.

The Vulnerability

The XSS flaw allows attackers to:

• Steal session cookies — Hijack user email sessions
• Read email contents — Access sensitive communications
• Send emails as the victim — Conduct phishing or BEC attacks
• Inject malicious content — Spread malware through email

Attack Vector

The attack is delivered through specially crafted emails. When a victim opens the malicious email in Roundcube, the XSS payload executes in their browser context.

Immediate Actions

1. Check your Roundcube version — Determine if you're running a vulnerable release
2. Apply patches immediately — Update to the latest patched version
3. Review email logs — Look for suspicious activity patterns
4. Warn users — Alert staff about potential phishing attempts

Long-Term Recommendations

• Keep webmail software up to date
• Implement Content Security Policy headers
• Use email security gateways to filter malicious content
• Conduct regular vulnerability assessments