If you upgrade TBB by overwriting an old one, it reads the old extensions.torbutton.updateNeeded

The check for a new Tor version opens a file on the file system for version information comparison.

There are scenarios where this file may be written to by an old version, or a exiting slowly version, as part of a TBB upgrade. (Or other scenarios where users do things totally unexpected and not recommended.)

Thus: when checking for newer versions, an old version is referenced, which will always claim to be out of date despite not being so.

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Possible improvements:

If the version check including the version of the build of the checker/writer somehow this condition would be avoided. Note that keeping the version of the author/checker in the file itself could lead to race conditions requiring some thought, while a version in the file path would not conflict. (e.g. old and new write to version.txt compared to old write to git-abcdef12-version.txt and new write to git-f00ff00f-version.txt)

Trac:
Username: anon