An API key is a unique series of characters that are included in a request to verify that the requesting system is allowed to communicate with the receiving system. If an API requires a key, the key is assigned by the API provider to an authorized API user. The user includes this key in every request made. The API key verifies the application making the call to the API and ensures that the calling application has the correct access to call the API. If the API key is not valid the API sends back an error response.
This rule applies at the API Specification level (OAS/Swagger).
Data Exposure: Attackers may exploit the lack of API keys to access sensitive data or resources exposed by the API. This could include personal information, financial data, or other confidential information that could be leveraged for malicious purposes, such as identity theft or fraud.