[Affected versions]: Firefox 56.0a1 (2017-06-18) Firefox 55.0b2 (20170615063713) [Affected platforms]: Windows 10 64-bit Ubuntu 16.04 32-bit [Steps to reproduce]: 1.Launch Firefox with a clean profile. 2.Install the following add-on https://addons.mozilla.org/en-US/firefox/addon/stylish/ 3.Navigate to https://userstyles.org/styles/141275/blacktube 5.Click “Install Style” blue button. [Expected Results]: The stylish theme is successfully installed [Actual Results]: - Nothing happens, the theme is not installed. - The following errors are thrown in Browser Console: mozilla::storage::Statement::BindStringParameter is deprecated and will be removed soon. (unknown) TypeError: browsers[i].contentDocument is undefined[Learn More] common.js:74:10 - See attached screencast. [Regression Range]: Last good revision: dabb46691f871fee43f2e39f4eedbd7fa7db79f2 First bad revision: 0975e301ce64d91d3287afe1f534ef0086333264 Pushlog: https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=dabb46691f871fee43f2e39f4eedbd7fa7db79f2&tochange=0975e301ce64d91d3287afe1f534ef0086333264 Looks like the following bug has the changes which introduced the regression: https://bugzilla.mozilla.org/show_bug.cgi?id=1256472

The error, "TypeError: browsers[i].contentDocument is undefined[Learn More] common.js:74:10", indicates that the add-on is attempting to use the shims in order to access the document of the browser. I honestly have no idea how bug 1256472 would have introduced this problem. I'll note that the add-on is apparently marked as e10s compatible, so it attempting to access a document like this (assuming it's on a remote browser) is expected not to work. Hey JorgeV, are we able to point the Stylish dev's at this one?

I sent a message to the developer.

Vasilica, I just tested with the latest addon version and it WFM on 55b5. Can you verify?

(In reply to Mike Taylor [:miketaylr] (55 Regression Engineering Owner) from comment #3) > Vasilica, I just tested with the latest addon version and it WFM on 55b5. > Can you verify? I am still able to reproduce this issue on Firefox 55.0b5 and also on Firefox 56.0a1 (2017-07-10) and Firefox 55.0b7 (20170706085221) under Windows 10 64-bit and Ubuntu 12.04 64-bit using Stylish 2.0.7. The same errors as those specified in description appear while trying to install a Style from https://userstyles.org/

Marking as won't fix for 57 because this is not a WebExtension and will not work by Firefox 57.