A linked session is an authenticated companion-device connection that lets a browser, desktop app, or other approved device access an account without re-entering the full login each time. In messaging platforms, it is the state created after a user pairs a second device with the account.
Linked sessions matter because they extend convenience and also extend risk. If an attacker steals the account, scans a pairing code, or abuses an already active session, they can send messages as the victim and exploit the trust of contacts. In real attacks, that can turn a familiar chat account into a malware delivery channel for malicious links or archives. Defenders should review linked devices regularly, revoke unknown sessions, and enable account protections such as device verification and strong authentication where available.