The detection rule 'Web Fraud - Password Sharing Across Accounts' is designed to identify potential fraudulent activity associated with user accounts sharing common passwords on the Magento2 e-commerce platform. It leverages HTTP request data to examine login attempts and applies specific regular expressions to extract usernames and passwords from the form submission data. The rule then analyzes the unique count of usernames that share the same password, flagging cases where the same password is used by more than five unique usernames. This anomaly detection can indicate potential password sharing or credential stuffing attacks. Given its nature, it emphasizes the need for careful implementation and context consideration, as it can generate false positives due to legitimate scenarios where multiple users might inadvertently use the same common passwords.