[quote=keskparane]I can enter input that will display an alert box with “HackThis!!” when I press submit.[/quote]
this is the thing you shall reach, but if you read the level-description, the task is: [quote=level]Bypass the filter and execute exactly this code:<script>alert('HackThis!!');</script>
[/quote]
here is a heavy weight on the word “exactly”. this means, after the filter progressed your input the string left has to be exactly the string given.