Elon Musk spent his Friday reposting criticism of competitors after the launch of the XChat app , a stand-alone messaging option for X users. “Signal, WhatsApp, Telegram, and iMessage all have serious security problems,” read a message Musk reposted, in part. “XChat is the only secure, encrypted messaging app.” Encryption experts I spoke with in the lead-up to this launch expressed cautious skepticism about XChat’s execution and defended other communication platforms, like Signal, as solid choices. One of XChat’s red flags is that users must connect an existing X account to log in and start messaging. “I'm a little suspicious of that, because the more data points you connect together about a person, the more you can track what they're doing,” says Maria Villegas Bravo, counsel at the Electronic Privacy Information Center . Bravo considers Musk’s past attacks on other apps to be worrisome and self-serving.…