Ubuntu Firefox addons breaking JS for some sites

[Rebecca Menessec]

WORKAROUND: Disable Unity Desktop Integration addon (no restart required)

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Test case: visit Mycroft Project site, attempt to install search engine plugin. Installation fails, redirects to http://mycroft.mozdev.org/jsreq.html ("JavaScript must be enabled to install a search plugin. If you have installed NoScript, you will need to allow this page to run scripts.")

Browser is Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:18.0) Gecko/20100101 Firefox/18.0 -- Firefox 18.0b4 from mozillateam-firefox-next PPA.

NoScript is installed, but .*\.mozdev\.org is whitelisted. Ghostery is blocking two trackers, but is not a factor. (Site still fails with Ghostery disabled.) ABP is enabled, but not blocking any content.

Error console content:

TypeError: this._mainWindow.gBrowser is undefined Source file: resource://unity/observer.js

(Not sure which package is related to resource://unity/observer.js , but assume it's xul-ext-unity || xul-ext-websites-integration)

Mycroft Project site can now install search engine plugins.

[Micah Gersten (micahg)]

I've confirmed this in a clean environment with no addons except for the ones shipped by default (global menu, ubufox, xul-ext-unity, xul-ext-website-integration) and when xul-ext-unity is disabled in Firefox 17, the site seems to work fine.

[Regular User (dot.ru)]

I confirm this and thank you for posting a workaround.