A few times in my latest game I've seen notifications that CS X or Y has declared war on someone, without any apparent change in their alliance status or in the wars their friends are involved in. But most bizarrely of all, Kuala Lumpur (allied with me at the time) was bought by Mongolia, who were friendly with me and with whom I've never been at war. I instantly got warnings from Isabella and Nebuchadnezzar that I'd attacked a state under their protection and, sure enough, when I looked at KL it was at war with me (with, however, a 'Make Peace' option because of course I wasn't at war with its ally). Has this happened to anyone else, and is it a bug? I'm not sure why this would have happened - the only war I was involved with at the time was with Rome, and I didn't see a notification saying that Rome had taken it as an ally in the same turn the Mongols did, nor did I see a "Kuala Lumpur has declared war on you" notification.