WebDAV Launcher Office Connector is broken in Firefox 43.0

Summary

The WebDAV Launcher Office Connector is not signed correctly and so does not install or run in Firefox 43.0 or greater. This is a recent change in Mozilla policy for extension signing.

Environment

• Firefox 43.0 or higher
• WebDAV Launcher 1.0.8.1-signed
• Windows, Linux or Mac

Steps to Reproduce

In Firefox

1. Go to Help > About Firefox
2. Make sure Firefox is version 43.0 or higher
3. Uninstall the WebDav Launcher

In Confluence

1. Go to a page with a Word document as an attachment
2. Click on the Word document
3. Click ... > Edit in Office
4. Click Ok for the Download box
5. Click Allow

See error

Expected Results

The document should load in Word

Actual Results

The Firefox add-on is not added. If it is already added, it will not work. The Add-on shows

The add-on downloaded from this site could not be installed because it appears to be corrupt.

The WebDAV launcher is disabled with the message

WebDAV Launcher could not be verified for use in Firefox and has been disabled.

Notes

This is a change in Firefox with Add-ons that are not signed correctly.

Workaround 1

1. Download the plugin directly from mozilla (using Chrome so it doesn't auto install) https://addons.mozilla.org/firefox/downloads/file/259818/webdav_launcher-1.0.8-fx.xpi
2. Go to about:addons, then Cog Menu > Install Add-On from file and select the .xpi file
3. Click Install on the pop-up box, then Restart

Workaround 2

1. Go the location bar and enter about:config
2. Click I'll be careful, I promise!
3. In the new Search field at the top enter xpinstall.signatures.required
4. Double click the entry to make it false

You can also put this entry in user.js in the firefox profile directory

user_pref("xpinstall.signatures.required", false);

The plugin will now work.