OK, not certain which part you do not understand so I will go by some assumptions of necessity.
TOR is a system by which you can (to a huge extent) use the internet very securely since they use a number of very secure providing locations which are configured to not allow anyone to track your location or the sites you visit. In layman’s terms.
MS-Windows users have been using this network for secure lines when they perform their OS “upgrades” to ensure they only download software that is supposed to be uninfected by malware, but it turns out that a few of the servers in the TOR network have been compromised, and have been modifying software on-the-fly that people have been downloading without the knowledge of the originating agency (M-soft) or the user since the indicators such as the hashtag verifier have also been compromised.
The result has been that instead of getting a “pure” upgrade from the MS people, they have been getting infected software without any warnings from the system or the virus-scanning utilities. This is why this information provided in the referenced article is so important, so people are informed that they might have unintentionally been infected despite the precautions taken to protect their machines.
Hope that is not too muddled to understand. :)