Thanks for the screenshots and the detailed reports (on the exact time / timezone this happened). We're digging through our logs to see which advertising partners might have had these sneak through so we can block them ASAP!
Thank you for the additional updates. We will dig into it further. In the meantime here are some additional instructions on how to prevent this in chrome:
An update: we've been spending a lot of time trying to find where this is coming from. It is also hard to test because it can sometimes be isolated to a small set of users for example, iphone only, on cellular data not wifi, in certain geo-locations, etc.
Please keep reporting if you're still seeing these (with a screenshot, exact time you saw it, and your time-zone). Thanks!