Flagvent 2025: Hidden 4

FV25.H4 - Waiting for Christmas

This hidden was discovered while solving the challenge: FV25.21 - Santa's Nice List

Solution

When we load the instance, we are greeted with a pleasant-looking loading screen:

This page only appears for a minute or so while the main challenge loads.

If we inspect the index.html source for the loading page, we notice some unusual whitespace near the end of the file, just before the closing </body> tag, with a suspicious pattern of tabs and spaces. This looks like whitespace-based steganography.

    </script>
	    	  	  	     	    	       	      	      	    
      	      	   	       	     	    	       		  	    
  	  	   	 	    		    	  	     
	   	       	       	 	  	  	   	    	     
       	       	    	      	   	       		 	 
	  	   	 	       	      	     

</body>
</html>

After a bit of research, we decided to try stegsnow on the index.html file:

stegsnow -C index.html

This reveals the hidden flag!

Flag:

FV25{h1dd3n_1n_5n0w}