Interactsh is an open-source solution for out-of-band data extraction. It is a tool designed to detect bugs that cause external interactions. These bugs include, Blind SQLi, Blind CMDi, SSRF, etc.
If you find communications or exchanges with the interact.sh server in your logs, it is possible that someone has been testing your applications.
You should review the time when these interactions were initiated to identify the person responsible for this testing.