Exchange: 0-day Exploit

You should monitor closely your Exchange with a XDR solution for compromise. Currently there is too much fog around this attacks. 

See: twitter.com/.../1575628998712774656

Just to clarify on the matter of "Could i be potentially be breached?". 

If you think, there could be an attack ongoing or something odd is going on in your network / company, do not hesitate to contact an incident respond team. Every minute counts in such scenarios. 

You will find Incident respond teams and services most likely on your government pages or you can contact Sophos Rapid Response. https://www.sophos.com/en-us/products/managed-threat-response/rapid-response

nakedsecurity.sophos.com/.../