Reusable secrets are credentials, API keys, session tokens, certificates, or other secret values that can be used again if they are exposed. In security, the danger is not only that a secret is stolen, but that it remains valid long enough to be replayed. If an attacker gets a reusable secret, they may authenticate as a user, access internal systems, call APIs, or move laterally without needing to break encryption or guess a password.
This matters because many breaches start with secret leakage in code repositories, logs, shared documents, screenshots, or build artifacts. Defenders reduce the risk by limiting secret lifetime, scoping permissions, rotating keys quickly, revoking exposed tokens, and using vaults or short-lived credentials instead of long-term static ones. In practice, incident response often focuses on finding every place the secret was copied and checking whether it can still be reused elsewhere.