"The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor, which exposes security-relevant information about the state of the product, such as whether a particular operation was successful or not." - Entry from the Common Weakness Enumeration
For more info visit <a href="https://cwe.mitre.org/data/definitions/203.html" target="_blank" rel="noopener noreferrer">CWE-203</a>