CyberGuard dictionary / Web Application Security
Session Hijacking
Session hijacking is the unauthorized use of another person's active session, often through a stolen or exposed session identifier.
In simple terms
Someone who gets a valid session token may be treated as the signed-in user until that token is invalidated.
Technical explanation
Tokens may be exposed through script injection, insecure transport, logs, or device compromise. Strong session generation, HTTPS, secure cookie settings, rotation, expiry, and revocation reduce risk; authentication checks alone do not stop reuse of a valid stolen token.
A stolen valid session can act as the user until it expires or is revoked. Protection includes secure transport and cookies, short appropriate lifetimes, anomaly review, and revocation after compromise.
Examples in practice
An attacker copies a session cookie from an exposed log and uses it to access the victim's account.
After a browser extension leaks a session token, the victim changes their password. The service also revokes existing sessions so the copied token cannot continue to work.
Why it matters
A hijacked session can grant access to data and actions without knowing the user's password.
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Sources and further reading
Published 2026-10-15 · Last updated 2026-10-15 · CyberGuard editorial content. Source links provide context; they do not imply endorsement.