Gregorio's change isn't what the changelog is referring to. That change is much much bigger and more involved, and will likely not be part of the quick 4.3/4.4 release. We're rushing this release because we need to get a smaller Windows installer out there ASAP. We might even settle on a 4.3.X version number and make that public, continuing more beta work in the 4.3.X series and releasing as 4.4 later on.

The changelog for 4.3.1 refers to something we broke in 4.3.0 while fixing something else that was broken since TigerTrees were introduced. The original code caused trees made out of files of a certain size to continuously fail creation (a rounding problem while dividing). We fixed this in 4.3.0 by using multiplication instead, but that caused an integer overflow. 4.3.1 contains a fix for the integer overflow. With any of the bugs, the tree would have been unusable (but would not have caused corruption). It basically would have caused any downloads of files of that size to not be able to verify against a TigerTree.