Just recently started seeing American Express ads that render in Safari vertically and seem to introduce a layer that prevents me from clicking on certain areas of the page outside the ad. I can't close or reduce the ad.
I had to repeatedly reload the page until a non-amex ad loaded so I could click "post new" and report this, then I had to tab around the page to get to the fields to enter the post, then I had to click preview post so that the upload attachment button would be lower on the page so I could click on it. The site is almost unusable. I've attached a couple screenshots.