Webmail abuse is the misuse of a browser-based email interface to read, modify, send, or impersonate mailbox activity without the owner’s consent. Because webmail runs inside an authenticated browser session, attackers who gain access to the session, exploit a web application flaw, or trick a user into running malicious web content may inherit the mailbox’s trust and permissions.
This matters because email is often tied to identity, password resets, internal approvals, and phishing. Abused webmail can be used to steal messages, create inbox rules, forward mail, hide alerts, or send believable messages from a legitimate account. Defenders look for unusual logins, suspicious session behavior, unexpected rule changes, and browser-side exploits such as cross-site scripting in mail portals. Strong patching, multi-factor authentication, session monitoring, and mailbox auditing help limit the impact.