WhatsApp vulnerability allows snooping on encrypted messagestheguardian.com
Easily the biggest story this week. The Guardian reported a 'backdoor' in Whatsapp's encryption, allowing for a third party to snoop on a conversation.
Even though Signal uses the same protocol, it does not have this issue, because it comes down to an implementation choice and Signal made it differently.
From what I understand, the choice is: what to do when a message is not yet received by the other party, but meanwhile the sender changes phones or sim card, which changes his keys. Do you drop the old message, or send it anyway with maybe a warning?
A third party could snoop by reading the old message before delivery, re-encrypting it, and sending it through without the receiver knowing.
And yes, it's crypto, so I'm butchering this explanation. Hackernews thread here. Moxie, creator of Signal, counters the article here.