Blocks more than it says it will.
Even blocks appropriate sites and the ability to uninstall it which is against FF ad-on policy.

Hello, I'm currently testing parental control systems to see which adult content tagging systems they respect. Even with "Examine Meta Content" turned on in the sensitivity settings, this extension fails to block websites based on various meta tags used by adult websites to identify themselves as such.
I've tested the following meta tags in use by adult websites and none of them cause the page to be blocked:
<meta name="rating" content="adult" />
<meta name="rating" content="mature" />
<meta name="RATING" content="RTA-5042-1996-1400-1577-RTA" />
<meta name="rating" content="RTA-5042-1996-1400-1577-RTA" />

This let me access at least two websites and various twitter accounts with explicit pornographic content which would otherwise have been blocked.

Also, all adult sites I've checked so far include at least one of these tags.

Don't waste your time, the password protection feature is behind a paywall.

A bloquer l'accès à des sites pour faire les devoirs de mes enfants. Demande de payer pour débloquer le site. Extension à fuir.

Not so smart.
- When opening links in a tab, the filter will block the current page instead of the new tab.
- Filtering is quite basic and will have many false positive and false negative.
- Access to extension settings is protected with a ugly workaround, not convenient at all, and not secured anyway.

Has been working well for me. You do have to pay for it, but it is well worth it. It is quite simple to use and exactly what I was looking for for the kids computers. Simple to install and manage from one place.

Password protects only the browser settings. It can easily be deactivated or removed from the puzzle icon - even with a password in place