This detection rule identifies potential open redirect vulnerabilities specifically related to the usage of the domain 'click.snapchat.com' in messages. The rule triggers when any links included in the message body point to 'click.snapchat.com' and are being sent from a sender whose email domain does not end with 'snapchat.com'. This type of URL can be exploited for credential phishing attacks, where attackers trick users into divulging personal information by redirecting them through seemingly legitimate links. With a medium severity rating, it is crucial for security systems to monitor this behavior as it can lead to significant security breaches if not addressed.