1. Start Firefox with e10s enabled. 2. Load the attached addon. 3. The addon opens a tab with some links and buttons. 4. Click on the links/buttons that claim to open "blob" URLs. Expected (without e10s): - A download dialog should be shown in all cases. When e10s is enabled, the <a download> case also fails: - When I click on <a download>, a load starts but never completes. - When I press Ctrl/Cmd-click to open in a new tab, the global JS console shows: NS_ERROR_DOM_BAD_URI: Component returned failure code: 0x805303f4 [nsIWebNavigation.loadURIWithOptions] at https://dxr.mozilla.org/mozilla-central/rev/4c05938a64a7fde3ac2d7f4493aee1c5f2ad8a0a/toolkit/content/browser-child.js#332

Was broken in Nightly 50 @ 2016-07-17, working as intended since today (Nightly 2016-07-18). Mozregression points to https://bugzilla.mozilla.org/show_bug.cgi?id=1279186 was responsible, which seems correct.

This issue has resurfaced. I cannot open blob urls (ie. blob:moz-extension://9b7041... ) I used to be able to take a screenshot with my extension https://addons.mozilla.org/en-US/firefox/addon/explain-and-send-screenshots/ and then click the Download button to open a blob url. I'm using Firefox 48.0.2.

The url in your comment isn't a valid blob url. However, if you think you're using blobs correctly and something isn't working, please open a new bug with detailed steps to reproduce.