Bearer tokens are compact strings that act like digital keys, granting access to systems and data once logged in. They're a core part of modern APIs and authentication flows, particularly in OAuth 2.0 protocols. However, bearer tokens are inherently risky as they don't verify who's using them, only that they're valid. Secure handling is essential to prevent risks such as token transmission over HTTP, insecure storage, leaking tokens in URLs and logs, long-lived tokens, missing or weak token validation, poor client-side token handling, overly broad token permissions, CSRF vulnerabilities, replay attack vulnerabilities, and insecure error messages. To use bearer tokens safely, always use HTTPS, store tokens securely, use short lifetimes, implement proper validation, monitor for anomalies, plan for compromise, minimize scope, implement token revocation/blacklisting, secure client implementations, log security events, and conduct regular security reviews to mitigate these risks and ensure application security.