This morning, upon upgrading my Firefox browser to the latest version (from 22 to 23), some of the key aspects of my back office (website) stopped working.
Looking at the Firebug log, the following errors were being reported:
Blocked loading mixed active content "http://code.jquery.com/ui/1.8.10/themes/smoothness/jquery-ui.css"
Blocked loading mixed active content "http://ajax.aspnetcdn.com/ajax/jquery.ui/1.8.10/jquery-ui.min.js"`
among other errors caused by the latter of the two above not being loaded.
What does the above mean and how do I resolve it?
I found this blog post which cleared up a few things. To quote the most relevant bit:
Mixed Active Content is now blocked by default in Firefox 23!
What is Mixed Content?
When a user visits a page served over HTTP, their connection is open for eavesdropping and man-in-the-middle (MITM) attacks. When a user visits a page served over HTTPS, their connection with the web server is authenticated and encrypted with SSL and hence safeguarded from eavesdroppers and MITM attacks.However, if an HTTPS page includes HTTP content, the HTTP portion can be read or modified by attackers, even though the main page is served over HTTPS. When an HTTPS page has HTTP content, we call that content “mixed”. The webpage that the user is visiting is only partially encrypted, since some of the content is retrieved unencrypted over HTTP. The Mixed Content Blocker blocks certain HTTP requests on HTTPS pages.
The resolution, in my case, was to simply ensure the jquery includes were as follows (note the removal of the protocol):
<link rel="stylesheet" href="//code.jquery.com/ui/1.8.10/themes/smoothness/jquery-ui.css" type="text/css">
<script type="text/javascript" src="//ajax.aspnetcdn.com/ajax/jquery.ui/1.8.10/jquery-ui.min.js"></script>
Note that the temporary 'fix' is to click on the 'shield' icon in the top-left corner of the address bar and select 'Disable Protection on This Page', although this is not recommended for obvious reasons.
UPDATE: This link from the Firefox (Mozilla) support pages is also useful in explaining what constitutes mixed content and, as given in the above paragraph, does actually provide details of how to display the page regardless:
Most websites will continue to work normally without any action on your part.
If you need to allow the mixed content to be displayed, you can do that easily:
Click the shield icon Mixed Content Shield in the address bar and choose Disable Protection on This Page from the dropdown menu.
The icon in the address bar will change to an orange warning triangle Warning Identity Icon to remind you that insecure content is being displayed.
To revert the previous action (re-block mixed content), just reload the page.