I have 7 but am still not getting it, I came across this at MacSlash.
A new announcement has come across Apple's security-announce list detailing a buffer overflow in StuffIt Expander. Apparently, "ZIP archives containing files with large filenames can cause a buffer overflow when expanded. Versions 6.5.2 and earlier of the Stuffit Expander utility contain this vulnerability." An update is available from SoftwareUpdate
If you have downloaded Stuffit 7 recently then you shouldn't have to worry about the bug. Stuffit 7 was released a few weeks ago, and then almost immediatly pulled to fix some problems and then re-posted about a week later. Basically the same situation as Toast 5.2
I think that 7 is the fix for the buffer problem in 6.5.x and before though.