In Twitter, goto Profile and Settings, then click Apps and Devices, now review any recent apps or devices that should be removed. If necessary, remove all cookies to Twitter because you might have a corrupt cookie. Do a web search on how to remove a particular cookie from your web browser for more information. Then log in after cookie purge and you should only get one new instance of that message from now on.
In Twitter settings for PC you will see Apps and Devices for you to review. Another thing to check is to make sure your Mozilla browser is not stuck in a update loop: Click settings button for Mozilla browser and then the Question Mark Icon seen at the bottom. Click the ABOUT link to check if your browser is current. If an update was needed, repeat this process to confirm your browser is UP-TO-DATE. Good luck anon!