NIS2011 - What does this pop up mean?

My wife received this pop up from NIS11.  What does it mean?

 

As no action is recommended, then I assume that NIS11 blocked Firefox from doing something harmful, right?  But Firefox and the system was not compromised?

 

Am I reading this correctly that some forum discussion message contained an attack link which she clicked on?

 

Thanks.

 

HTTP Zombie Exploit Toolkit Request