The 'Hotfix prerelease' which implements the DAO rescue hard fork spec (https://blog.slock.it/hard-fork-specification-24b889e70703#.igh9b62hy)
Essentially this is just a transfer from the set of predefined accounts (the DAO, its children and their extraBalance contracts) to the specially created Withdraw contract (https://live.ether.camp/account/bf4ed7b27f1d666546e30d74d50d173d20bca754) at the beginning of the block #1920000 (i.e. before processing any transactions from this block)