The product implements an authentication technique, but it skips a step that weakens the technique.
Authentication techniques should follow the algorithms that define them exactly, otherwise authentication can be bypassed or more easily subjected to brute force attacks.
This weakness can lead to the exposure of resources or functionality to unintended actors, possibly providing attackers with sensitive information or allowing attackers to execute arbitrary code.
Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)