HiSteps to reproduce:
* enable AdBlock Plus in Firefox
* add a rule for `event.gif` (Tools/AdBlock Plus/Filter preferences/Custom Filters, add filter group "test", per today I can not use the 'Select Files' button at the upload wizard.
https://commons.wikimedia.org/wiki/Special:UploadWizardadd filter "event.gif")
* call `mw.eventLog.logEvent`
Cause seems to be the adding to the web-interface of a button to select files from Flickr.
Now only the Flickr button can be used, which I don't need.Expected result: call returns a failing promise
Actual result: call throws an exception
RegardsApparently navigator.sendBeacon can do that (just like non-CORS AJAX requests) when the URL is blocked by the browser's security policy.