By following the first link on the site you've mentioned I came to a short document describing why Web Security and others has been blocked. This document refers for detailed information to this support article. I think this document provides most of the information you want to know in detail. To cite:
Once a block is implemented, Firefox will block the unsafe add-on from loading. Blocks can be issued at varying levels depending on the severity of issues found.
- Soft blocks disable an extension by default, but allow you to override and continue to use the add-on. Soft blocks are issued for non-malicious add-ons.
- Hard blocks disable an add-on and do not allow you to enable it or override the block. Hard blocks are used when add-ons are found to be malicious.
- Click-to-activate blocks disable a plugin by default, but allow you to enable the plugin for particular sites. This type of block is issued for non-malicious plugins.
I cannot see any information how it deals with already disabled plugins. But I'll guess it works the same as with previously enabled plugins, i.e. depending on the type of block you might be able to re-enable it or not.