Single Sign-On (SSO)
One login that establishes a session trusted across many applications, instead of a separate username and password for each — the master session an IdP issues once and every app checks after.
aka: SSO
SSO’s core risk is exactly its convenience: one compromised master session opens every connected app at once, so how long that session lives and how cleanly it can be revoked matter as much as the login itself. Single Logout — ending every app’s session when the master one ends — is the neglected half most implementations get wrong.