A shadow API key is an undocumented, forgotten, or otherwise unmanaged API credential that remains active within an organization's systems. These keys are not tracked or maintained, making them vulnerable to unauthorized access and exploitation by attackers. Shadow API keys often arise when developers create test environments, temporary integrations, or fail to properly decommission old services. Since they are not included in official inventories or security audits, these keys can provide a hidden entry point for cybercriminals, potentially leading to data breaches or system compromise. Regular API key management and periodic security reviews are essential to detect and eliminate shadow API keys.