Research Reveals CSS Injection Attacks Threatening Webmail Security

New research presented at Black Hat USA 2026 details CSS injection attacks capable of bypassing webmail client security measures. These attacks could allow malicious actors to steal user credentials, exfiltrate authentication tokens, and compromise accounts on major platforms such as Outlook, Gmail, and Yahoo Mail. This development underscores a significant vulnerability in widely used email services, necessitating enhanced security protocols and user vigilance.