UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.62 Safari/537.36

Steps to reproduce the problem:
 1.  Go to https://manishjethani.com/examples/closedshadow
 2.  Observe the blinking ad
 3.  Install Adblock Plus 1.13.4 or newer
 4.  In the extension's options, add the custom filter manishjethani.com#?#.info:-abp-contains(Flashy Ad)
 5.  Reload the page
 6.  Observe that the ad is hidden
 7.  Wait for 5 seconds and observe again

What is the expected behavior?
The ad should remain hidden.

What went wrong?
The ad is back!

Did this work before? N/A 

Does this work in other browsers? Yes

Chrome version: 62.0.3202.62  Channel: n/a
OS Version: OS X 10.12.6
Flash Version: 

See the script, it removes the ad from the light DOM and adds it to the shadow DOM. As the shadow root is closed, there's no way for the ad blocker to access it to hide the ad again.

Please note that Adblock Plus 1.13.4 doesn't try to access the shadow DOM at all, closed or not, but that's precisely because it would be easy for page authors to circumvent it by using a closed shadow DOM. We would like to have access to the shadow DOM, even if it's closed, from the extension. It's reasonable as extensions work on the user's behalf, an extension should be able to modify any part of the DOM.
 

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