Various vulnerable add-on versions has been blocked for your protection.

Why was it blocked?
A security vulnerability was discovered in old versions of the Add-ons SDK, which is exposed by certain old versions of add-ons. In the case of some add-ons that haven't been updated for a long time, all versions are being blocked.
Who is affected?
All users who have any of the affected versions installed.
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.