This is an old revision of the document!
Damien Vizár pointed out in this discussion on the Cryptographic Competitions group that one can trivially forge valid ciphertext/tag pairs for input where the last block of associated data is not a multiple of the block length. This is due to the padding rule for the last associated data block: rather than using 10* padding, padding is done using only zeroes. This can be fixed using 10* padding instead.