Cannot receive result from canLoad within some iframes

[el1t]

Describe the issue

When an iframe is created through document.write and src is set to a JS object, safari.self.tab.canLoad() will return undefined to while within the iframe. This causes some requests to slip through.

One or more specific URLs where the issue occurs

https://iframe-example.surge.sh

adgear example: http://noovo.ca
note this does not occur in https://iframe-example2.surge.sh

Steps for anyone to reproduce the issue

1. Visit site that creates iframe in a particular manner

Your settings

• Safari version: 10.0.3
• uBlock Origin version: 1.10.5.9
• MacOS version: 10.11.6

Your filter lists

Default (irrelevant)

[el1t]

Sometimes self.top.safari is used when self.safari is not defined (for example, https://iframe-example.surge.sh). For whatever reason, Safari expects self.safari to be defined always.