Microsoft has released an out-of-band security update for a serious and actively used number of exploits on Microsoft Exchange. They named it Hafnium.
The following versions of Exchange Server are affected:
- Exchange Server 2013
- Exchange Server 2016
- Exchange Server 2019
Is this attack connected to the SolarWinds attack?
Microsoft has said that it has seen “no evidence that the actor behind SolarWinds discovered or exploited any vulnerability in Microsoft products and services.”
You need to follow the latest updates recommendations of Microsoft here https://techcommunity.microsoft.com/t5/exchange-team-blog/released-march-2021-exchange-server-security-updates/ba-p/2175901