I created a random mashup generator which finds codeforces problems that aren't solved by any of the users in a group. It automates the mundane task of finding problems not solved by a particular group of users. You can use this to host mashup contests with your friends or use it for yourself.
Here's a link to the website random mashup generator
For any bugs or feature requests feel free to comment down below.
If you like the project, consider giving it a star on Github
Finally, I would like to thank Sakuna for giving me the inspiration to this project.