Last modified: 2010-05-03 08:49:10 UTC
When an IP globally blocked with [[m:Special:GlobalBlock]] reaches its expiry date, it stops being enforced but otherwise continues to be active. It is listed as an active block on [[m:Special:GlobalBlockList]], [[Special:GlobalBlock]], and in API results. I reproduced this by globally blocking 127.0.0.1 for 5 seconds. As of this report 15 minutes later, it's still marked active.
Based on the title it sounds like this is referring to a regression(/s), tagging as such (+code-update-regression).
Those blocks should be purged the next time a global block is made. I've hidden them from Special:GlobalBlockList in r65840, which can be deployed if necessary.