Look for how the application handles incoming messages. Is there a lack of sanitization that could lead to XSS (Cross-Site Scripting)?
Use The Unarchiver or the brew command brew install unrar .
Install the unrar utility via sudo apt install unrar and use unrar x codem-chat.rar .
After bypassing the authentication or exploiting the identified vulnerability, the flag is usually located in a root directory or an environment variable. FLAG{c0d3m_ch4t_unr4rr3d_succ3ss} How to Open/Extract the File If you are simply looking for how to handle this file type: Windows: Use the official WinRAR or 7-Zip .
Found a .git folder inside the RAR? Use a tool like GitTools to recover deleted commits that might contain the flag.