iMessages sent from my account that I did not write
Last night I noticed a couple of messages sent from my Messages account to two conversations with friends from days and weeks ago, messages that were direct replies to the last messages in the conversations. They were blue bubble messages, too, so not SMS. I did not write them. I immediately suspected my account was compromised so I changed my password and checked if any unknown devices were using my AppleID. I didn’t find anything suspicious. I’m trying to figure out how my account could have been hacked. I use a password manager: all my passwords are unique, long, and random. I have 2-factor authentication on. I received no notification of a device asking for an authentication code or an email from Apple about a password change. Some of my information —birthday, my appleID email, and phone number— were compromised in the most recent T-mobile hack, so I was concerned a bad actor may have used that information through Apple Support to gain access to my account through Account Recovery, pretending to be me. But I received no email or other indication that my password had been changed and I was not logged out of any of my devices, which I believe should have happened if someone reset my password and gained control of my account. Neither of the mystery messages were malicious. I’m just trying to wrap my head around what may have happened and how, and hoping someone with more security knowledge can help me figure this out. Thanks.
iPhone 13 mini, iOS 16