By: smashmaster

Tags: Web ImaginaryCTF-2022

Problem Description:

Apparently one of these buttons isn't useless...


Reveal Hints Word processing is overrated, go back to text processing (no offense).


We present several solutions for eliminating a massive clustering of clickable buttons that violate onClick execution time policies.

Local mirroring + Text Editor + Find and replace

Let’s copy this into our own local html file that we have control over (using stackblitz for a clean and reproducible).

stackblitz is a cool html editor that works entirely in browser even with full stack apps using the power of wasm

<button class="not-sus-button" onclick="notSusFunction()">.</button> seems to be the pattern so we’ll find and replace it away. Hey so now the first button is the button we need!

stackblitz however lacks a menu accessible find and replace

View Source + Find

Find tool on “ictf”. We are able to find which string is the flag without the wrapper due to how it says “flag” inside. a wild flag appeared

Global scope search!

In order to be callable from the html attribute onclick, the functions must be in global scope. As before when viewing the source code we see the not so useful function has sus in it. Perhaps the function we want also includes the character sequence sus in it? Object.keys(window).filter(prop => prop.toLowerCase().includes("sus")) finds everything with sus in it in global scope Breaking it down.

  • Every variable declared that doesn’t go out of scope like when it is in a function, ends up on the window object.
  • We use the special method Object.keys to list properties existing on window.
  • We filter by a condition that evaluates to true if the property contains “sus” after being all lowercased. After that we just run the function!

CSSed away

By setting display to none in css on a selector with attribute that selects all buttons with an onclick of notSusFunction() we can hide all the not sus buttons so that the one we need goes to the top. chrome lagged when I clicked the add style button


This challenge tested our ability to find a distinct needle in a giant haystack. We used a variety of methods to eliminate out the stuff we didn’t need like find and replace and selectors. We also looked for exposed functions directly in the javascript.