I'd want to want to look at a few advisories to see which bits are constant and which bits are variable, then I'd hopefully be able to identify sub-sections by it's 1st line.
It also appears that each sub-section is separated by blank lines, so that's also a hint. I did something similar once or twice in the past and used a separate subroutine for each sub-section.
If you ask them nicely, they may even have a format definition doc. It certainly looks like a format that's designed to be readable by humans and programs.
Cheers
Chris