I have recently started having an issue where I cannot actually select a new branch from the dropdown that appears when I edit the title of a PR. I can open the dropdown, and I see all the branches available in the repo. However, when I actually click on a branch name nothing happens. I have tried clearing all site data and restarting my browser, but that did not change anything. There are no errors on the browser console when I try this, though there are three Content Security Policy errors that occur when I load the page (or any other page on GitHub). I’m at a loss as to what could be causing this.
Browser: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:61.0) Gecko/20100101 Firefox/61.0