How to edit CGI script website files as a user?

Good Afternoon,

This is just a hypothetical question. Let's say we have a website built using CGI scripts. I find a folder within it (for ex; http://ift.tt/1NylwnC) and it has some basic text files. When I enter this URL on a browser, I am able to see the file "link.txt". I also know that the website is running on Apache Tomcat.

My question is, how do I (as a user) edit this link.txt file? What tools should I use? Looks like SSH, Telnet, SCP, FTP are not working. Is there a way to edit it using a browser plugin or something? (and I mean without a root username/password - how to hack root username/password?)

This is a good question, so please don't downvote.

Regards