A man-in-the-middle (MITM) attack consists of a victim, a website the victim would like contact with (such as a bank), and the attacker. The attacker inserts themselves between the victim and the targeted website with the intention to steal personal information such as login credentials, or bank account and credit card numbers. MITMs have consistently been an active development strategy for hackers.
I wrote about this for Avast’s blog here. One way to prevent this exploit is to use a secure browser (such as one from Avast or Brave).
A good discussion about MITM attacks along with some great samples can be found in this post on CSO: https://www.csoonline.com/article/3340117/man-in-the-middle-attack-definition-and-examples.html