Just updated from SourceTree 2.5.5 to SourceTree 2.6.6. After startup, SourceTree shows yellow flag that says "A newer version of Git-LFS is available"
I check in my SourceTree installation folder, and see two different git-lfs.exe exists.
One is v2.0.2, which is the one SourceTree is detecting. The other is v2.4.2, which is not being detected.
For some reason, the update to SourceTree v2.6.6 didn't properly cleanup the older git-lfs.exe
New version was in C:\Users\<my user name>\AppData\Local\Atlassian\SourceTree\git_local\mingw32\bin\
Old version was in C:\Users\<my user name>\AppData\Local\Atlassian\SourceTree\git_local\mingw32\libexec\git-core\
All the other files in the same directory as the old version all seemd to be current, e.g. git-*.exe files from embedded Git were all for version v188.8.131.52 (the current version)
To me it seems like something has changed with the placement of git-lfs.exe, and the updater is not cleaning out the old git-lfs.exe when it runs.