Hi, I am experiencing the same problem. After installing the security update, all cookiejars stopped working. They are 0 bytes on the filesystem.
Rolling back to 5.4.36-0+deb7u3 fixed the problem for us too. Thanks for investigating this. -- Kind Regards, Met vriendelijke groeten, Meilleures Salutations, Tommie Van Mechgelen ~ don't believe the hype ~