I contacted Airbnb Support and got two different responses from different people:
Hi Sally Kerecia here from the Airbnb support team. The messages you're getting with verification codes are due to a glitch in the system. It's nothing you have to worry about.
Then the next day:
Hello Sally,
My name is Anne, Support Ambassador from Airbnb.
I appreciate your patience about this matter and I apologize for the inconvenience that you've encountered but rest assured everything will be taken care of.
Thank you for reaching out to us, and for letting us know about this issue as soon as possible for us to immediately assist you.
I'm sorry you've received many verifications without your request. I understand that you are concerned about the security of your account. Please know that your information is safe with us.
We were able to receive reports about this, and we’re working to resolve it as quickly as possible. I just want to set your expectations as well that I'll be needing to report this concern of yours to our technical team and for that I'll be needing to close your ticket in able for them to have full access with your account.
Your privacy and security matters to us. We take all precautions to keep your information safe, and we adhere to the highest industry security standards.
Thank you so much for your patience and understanding about this matter.
Regards,
Anne.
Still getting the infuriating messages in the middle of the night.