Fuzz the Application with the below wordlist

https://github.com/danielmiessler/SecLists/blob/master/Discovery/Web-Content/CMS/sharepoint.txt

Sharepoint Enumeration and exploitation tool

https://github.com/MayankPandey01/Sparty-2.0

Check misconfiguration

https://github.com/H0j3n/EzpzSharepoint

Check the list of latest RCEs