Classic - Unknown error breaks all subsequent network requests

[zakius]

Describe the bug

In extension I am maintaining it's required to perform multiple HTTP requests. In most cases when request fails everything goes smoothly, but for some class of errors both XHR and Fetch break and start throwing Content Security Policy: The page’s settings blocked the loading of a resource at [URI] (“default-src moz-extension://[extension id]”). errors for every single request attempted, creating new XHR objects doesn't help, only reloading the extension unlocks the ability to perform requests.

To Reproduce

As I'm not able to pinpoint class of errors that cause this issue I can't provide reliable way to reproduce

Expected behavior

Failed request shouldn't make other requests fail

Additional context

thanks to mozregression I pinpointed 2017-08-09 to be the first good official build, earlier ones also had this issue.

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[zakius]

New discovery: it seems to be happening on requests returning 404