An important regression was unluckily reported a few hours *after* the release went out, so now we have to immediately bump it up to v1.4.3 with a hotfix. No special upgrade instructions but updating the code are necessary https://github.com/tootsuite/mastodon/releases/tag/v1.4.3
We are truly sorry for the inconvenience. We have lots of systems to assure code quality, review changes, test releases, but sometimes errors still slip through the cracks.