They are different addons. The malicious one that was blocked was called "one tab". Because it has been blocked, it will not run in firefox even if it is installed. The malicious addon did not come from mozilla's addon store (addons.mozilla.org) - instead, it was installed by other software that people downloaded. The one at addons.mozilla.org is called "oneTab". It is a different addon, and is not malicious (addons from addons.mozilla.org are reviewed by mozilla before being published to ensure they are safe).

Thanks! That's exactly what I needed to understand. I'm safe :)