MatchTheRegex

MatchTheRegex

How about trying to match a regular expression The website is running here.

Solution

1. First we access the challenge using the provided url.
2. We then get a web page asking for a valid input with input being parsed through a text box.
3. Now, lets try random strings.
4. The next step would be checking the source code to understand how the input is parsed.
5. Press ctrl+u to view page source.
6. Navigate to the javascript where the logic is coded.
7. The code has a function send_request() which retrieves the value entered in the input field with the id “name”, it then sends it as a query parameter in a fetch request to the /flag endpoint, and displays the value of the “flag” property from the response in an alert box.
8. As the title suggests, the input should match a particular regex to pop out the flag.
9. Checking the code again, we get a javascript comment that shows the regex ^p.....F!?
10. The comment shows a regex of a string with 8 characters that starts with p and ends with F and the ! is optional.
11. I then come up with a random string piqwerF that I use to pop out the flag.

Eazy Peazy. Remember to stay vigilant in the digital wild west. Happy Hacking.