Siri sent a text without permission

While driving alone in my car, I received a call from a former coworker who said I texted him. The text message was a single word, “Transformation.” The message also indicated that Siri sent the message.

I did not instruct Siri or said anything while I was driving.

I researched this with the Apple Community and found another incident like this one. The replies questioned the poster, saying she must have allowed another person access to their device because Siri can’t be hacked.

Is there a bug with Siri?