I am quite new to C programming, having only really been introduced to it in the context of software vulnerabilities. I am taking part in a CTF challenge, and have the following C program running on linux. There are numerous inboxes, but I am only allowed to use user Alice, who is not privileged, to find the flag, which is found in someone elses inbox. I am thinking there is an issue with how the program reads and writes to files, but I cant quite find it. I am hoping someone on here might be able to find the vulnerability in the C code? The entire program can be found at c program - Pastebin.com