YouTube downloader has been blocked for your protection.

Why was it blocked?
The add-on has a mechanism that updates certain configuration files from the developer’s website. This mechanism has a vulnerability that can being exploited through this website (downloader.yt) to change security settings in Firefox and/or install malicious add-ons.
Who is affected?
All users who have this add-on 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.