Default Tab has been blocked for your protection.

Why was it blocked?
Old versions of this add-on had been silently installed into users' systems, without showing the opt-in install page that is built into Firefox.
Who is affected?
All users who have this add-on installed. Users who wish to enable it again can do so in the Add-ons Manager tab.
What does this mean?

The problematic add-on or plugin will be automatically disabled and no longer usable.

When Mozilla becomes aware of add-ons, plugins, or other third-party software that seriously compromises Firefox security, stability, or performance and meets certain criteria, the software may be blocked from general use. For more information, please read this support article.