In cybersecurity, a 'hardcoded key' refers to a secret password, cryptographic key, or authentication code that is directly written into the source code of software or firmware. This practice is risky because if attackers gain access to the code, they can easily discover and exploit the key, potentially compromising the security of the entire system. Hardcoded keys are considered a significant vulnerability, as they are difficult to update or revoke once the software is deployed, making it easier for unauthorized users to bypass security controls.