Second order issues are being introduced using one request, while their effect is on response of different, unrelated request. This extension aims to support tester with semi-automated solution towards discovering such issues.
This functionality can be accomplished using Burp alone, but I personally find this extension way to be both quicker and less distracting when conducting tests.
Requires Java 8.
This extension DOES NOT require Burp Suite Professional
https://github.com/hvqzao/burp-second-order/releases/download/1.0/second-order.jar