Most cracked versions of Burp Suite require a custom "loader" or "keygen." These executables are frequently embedded with Remote Access Trojans (RATs) or info-stealers. While you are busy scanning a target for vulnerabilities, the software could be silently exfiltrating your browser saved passwords, SSH keys, and session tokens to a command-and-control server [1, 2].
Cracked versions are often outdated. Burp Suite receives frequent updates to handle new web protocols and vulnerability research . burp suite pro cracked github free