Generally Ubuntu Linux hasn't allowed new minor point releases of software to be sent down as stable release updates (SRUs) once the Ubuntu release ships, but there's been many exceptions, and now Ubuntu's Technical Board has agreed to make changes to make it easier to send down micro-release updates as well as offering new features to existing LTS (Long-Term Support) releases.

Ubuntu will begin allowing new upstream micro-releases for all Ubuntu packages, assuming the software in question has a proper continuous integration setup to ensure the quality of every commit of every release. Additionally, there must be tests concerning API/ABI stability as to not accidentally break that for a current Ubuntu release. The changes on the new Ubuntu SRU policy can be found via this Wiki diff.

The stable release update policy was also updated for allowing new features in Long-Term Support releases. New features will be allowed as long as they don't change the behavior for existing LTS installations and has only unintrusive changes with minimal regression potential.

More details on their new policies regarding micro-releases and new features for LTS versions of Ubuntu can be found via this mailing list announcement by Martin Pitt.