All application developers should be aware that Facebook today pushed live changes to the session key formats. This could require developers to update their applications to continue functioning correctly.

Facebook’s Platform team writes:

Please note that the session keys are longer than before, and the set of possible characters in the session keys include all alphanumeric characters (case-sensitive), along with ‘-’, ‘_’ and ‘.’.

If you notice any problems with session keys or signatures, please check first that your code accommodates the changes above. Bugs can be filed at http://bugs.developers.facebook.com/enter_bug.cgi.