The product stores sensitive information in cleartext in a file, or on disk.
The sensitive information could be read by attackers with access to the file, or with physical or administrator access to the raw disk. Even if the information is encoded in a way that is not human-readable, certain techniques could determine which encoding is being used, then decode the information.
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.)
CVE-2001-1481Cleartext credentials in world-readable file.
CVE-2005-1828Password in cleartext in config file.
CVE-2005-2209Password in cleartext in config file.
CVE-2002-1696Decrypted copy of a message written to disk given a combination of options and when user replies to an encrypted message.
CVE-2004-2397Cleartext storage of private key and passphrase in log file when user imports the key.