The data is rarely from a single new breach. Instead, it is a compilation of information from older leaks, "stealer logs" (data harvested by infostealer malware), and phishing campaigns.
These "MIX" text files are primarily used by attackers for credential stuffing , where automated scripts try combinations across various websites to gain unauthorized access to accounts. 107K MIX.txt
Records are often formatted as email:password or username:password in plain text to allow easy processing by hacking tools. Associated Risks The data is rarely from a single new breach