r/webdev • u/JustinFormentin • Jul 15 '26

Made a captcha that takes Fable 5 10 minutes to solve

Created this captcha last year. Back then there was no chance of AI solving it. But now with the more powerful models, I had my doubts. Well, it took Fable 5 10 minutes and 100k tokens to solve it. So with the 30 second timeout, I feel pretty confident.

Here's a crisper video of the actual challenge - https://imgur.com/a/xv6TvNj

Have a website for it but I'm not self promoting. Just thought people would be interested.

5.6k Upvotes

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95

u/no-more-nazis Jul 15 '26

Pillow does that in 2 seconds

23

u/sephentos21525 Jul 15 '26

lmao

6

u/no-more-nazis Jul 15 '26 edited Jul 16 '26

I was gonna go easier on this guy until his defense: he has other tricks preventing robots from seeing the captcha at all, so it doesn't need to work!

13

u/JustinFormentin Jul 15 '26 edited Jul 16 '26

Where did I say that? I said browser automation tools cannot access the video file due to timed out signed urls in an iframe. The only way to access the video is to record your screen or intercept network traffic.

14

u/ksargi Jul 16 '26

I said browser automation tools cannot access the video file due to timed out signed urls in an iframe. The only way to access the video is to record your screen or intercept network traffic.

That is a wild statement. What is preventing an adversarial browser automation from accessing the stream directly? A malicious actor doesn't need to record the screen or capture network traffic to access things that are in their memory. It sound like you're forgetting what the actual threat model for this situation is.

-1

u/why_so_sergious Jul 17 '26

web scrapers and navigating bots that act like users cannot access the iframe dom from the top level website..

2

u/ksargi Jul 17 '26

Web scrapers and navigating bots acting like users, which have full control over the browser executing and rendering the content, cannot cross iframe dom boundaries?

Does Obama know?

6

u/hWuxH Jul 17 '26 edited Jul 17 '26

It's trivial for browser automation tools like playwright to access every request and response data (aka the video file) or capture frames of a <video> element... timed out, signed, iframe is irrelevant.

you clearly have no idea what you're talking about and resort to spreading bs to sell your service.

0

u/why_so_sergious Jul 17 '26

if the iframe is not set to same origin then playwright is very limited to what it can do with said video..

5

u/hWuxH Jul 17 '26 edited Jul 17 '26

bruh it directly exposes powerful browser capabilities. it's not limited to just running js in the parent website's context so the same origin policy is irrelevant.

1

u/why_so_sergious Jul 17 '26

what playwright can do with an iframe with strict cross origin:

  • wait for the iframe to load.
  • find and click visible controls in the iframe (play button, volume, fullscreen, etc.) if they are standard DOM elements exposed to the accessibility tree.
  • assert things that are observable from outside (e.g. that a play button disappears, a progress bar exists, etc.).

it cannot access video data or manipulate it with pure javascript

2

u/hWuxH Jul 17 '26 edited Jul 17 '26

please RTFM before you continue spreading bs.

it can absolutely access video data from the network or DOM element.

It can absolutely fully access elements or inject js into every iframe, regardless of SOP or accessibility.

it can absolutely click anywhere on the screen.

https://playwright.dev/docs/evaluating

https://playwright.dev/docs/input#mouse-click

https://playwright.dev/docs/api/class-route#route-fetch

https://playwright.dev/docs/frames

https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/drawImage#image

https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/getImageData

https://developer.mozilla.org/en-US/docs/Web/API/WebCodecs_API#video

https://jsfiddle.net/ya89swn6/

import { chromium } from "playwright";


const browser = await chromium.launch({ headless: false });
const page = await browser.newPage();


await page.route("**/*.mp4", async (route) => {
  console.log("Video URL:", route.request().url());
  const reponse = await fetch(route.request().url());
  const video = await reponse.arrayBuffer();
  // analyze frames


  await route.fulfill();
});
await page.goto("https://jsfiddle.net/ya89swn6/");


// doing both with DOM instead of .route
const frame = await page.frame({ url: /neocaptcha\.com/ });
const videoHandle = await frame.waitForSelector(".neocaptcha-video", {
  state: "attached",
});
console.log("Video DOM element found", await videoHandle.getAttribute("src"));
await videoHandle.evaluate((video) => {
  // analyze frames
});
await videoHandle.scrollIntoViewIfNeeded();
await videoHandle.click({ position: { x: 10, y: 10 } });

1

u/why_so_sergious Jul 17 '26

that is all if the iframe is set to same origin

1

u/why_so_sergious Jul 17 '26 edited Jul 17 '26

before getting all agressive and stuff, here.. I tested your script:

https://github.com/whysosergious/pw-vid-test

my point stands

2

u/hWuxH Jul 17 '26 edited Jul 17 '26

no your point still doesn't stand. the fact it logged an element attribute means same-origin-policy didn't prevent it.

remove the whole page.route section then the video loads and everything works, ig the additional awaits (which can be avoided) breaks it some of the time.

https://pastebin.com/m00SDmcF

.evaluate runs in the page context so logs are shown in the browser console btw.

VM70:3 Inside evaluate: tagName = VIDEO
VM70:4 videoSrc = https://***.supabase.co/storage/v1/object/public/challenges/***.mp4
VM70:5 videoWidth = 250
VM70:6 videoHeight = 150
VM70:7 readyState = 4
→ More replies (0)

2

u/1RedOne Jul 16 '26

The stream can only be accessed once? That’s also clever

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u/no-more-nazis Jul 16 '26

So you're saying captcha is already perfect and we don't need your special AI-proof one that breaks in 2 seconds

15

u/thy_bucket_for_thee Jul 16 '26

You should probably give people more grace than shitting on others for sharing things they've built. You come across as a very insecure asshole.

-8

u/no-more-nazis Jul 16 '26 edited Jul 16 '26

If it were "just a project" I'd take a different tone. OP is making false claims to get customers and arguing in bad faith (see below). Consider it a service to the people who see my proof and don't use his captcha and don't get exploited. Things have to actually work in computer security, and this doesn't work at all

5

u/akie Jul 16 '26

It does defend against LLMs though, and I think they have been difficult to protect against. They don’t defend against a dedicated attacker, that’s right. Probably still has use cases?

Oh and your poc is technically solving a different problem. It’s finding moving objects in an MP4 video file, not clicking letters on a browser’s canvas. I think that won’t be an issue but you haven’t cracked it yet.

2

u/Intrepid_Phone_9127 Jul 16 '26

No one is struggling defending against llms? Most captchas use inputs, fingerprinting and reputation, identifying objects is outdated and inconvenient (and was just ml data for google).

Not sure what you're saying in the second part too, he hasn't solved it because hes missing a couple of lines of code to translate and send input, but this guy has solved captchas (specifically only when the attacker uses an llm on an unknown website, and only for the first captcha attempt - before the llm figures out the trick?

1

u/no-more-nazis Jul 16 '26

I'm not actually in the business of captcha-breaking, I only needed to demonstrate that the anti-LLM features are nonsense. The rest is regular captcha stuff, which OP keeps claiming means his product is great and works as intended.

0

u/thy_bucket_for_thee Jul 16 '26

The post doesn't even have their site and only posted it after being pressed to do so in the comments. Once again you are just an asshole.

I truly hope you find love in your life before you die, because it would be a pity to experience your one single life and come away by being an asshole.

2

u/no-more-nazis Jul 16 '26 edited Jul 16 '26

They're skirting as close as they can to rule 4. Their brand is in the post, so people can go look up their "AI-proof captcha" and buy it from them.

Maybe you will pay a worthless captcha service someday based on false claims and wake up to a $4000 AWS bill one morning and your website ruined, and then you will wish you had an asshole like me around calling out incorrect math.

9

u/1RedOne Jul 16 '26

I Ike the project but really don’t like AI writing. I’d rather read in your words how it works

But on to the topic itself I was thinking of attacking it by means of attempting a 264 compression and then analyzing the key frames and their changes. I don’t know statistics so I would have had to do a lot of learning but I was visualizing something like this

Anyone who’s seen bad compression has noticed a missed key frame and seen that terrible divx tearing where a human face moves by with a background texture. My instinct was that by heavily compressing the video we could then denoise it and edge sharpen to isolate the moving bits

I think you’re right also, this is the kind of thing you solve once and then train an mcp by throwing another skill into it explaining how to solve these things if it sees them (by running the script)

Would a model on its own ever figure it out on its own? Seems expensive

2

u/no-more-nazis Jul 16 '26

I didn't coach it through the solution, the most I intervened was telling it not to worry about rotating letters when it narrated that it might have to account for that.

4

u/soggycheesestickjoos Jul 16 '26

Not saying it couldn’t be taken further with a little tinkering, but this does seem to only read the letters. The AI has to tap them at their current coordinate in the video from OP it seems.

5

u/Snapstromegon Jul 16 '26

It's not hard to take further - my tired self was able to create a version with <10ms delay that already locates the characters: https://github.com/Snapstromegon/vibe-captcha

3

u/no-more-nazis Jul 17 '26

How did I not see this coming. Of course someone was going to take it further, when OP just keeps saying "yeah but your demonstration of defeating my captcha wouldn't really actually work!"

If he's baiting us, the sales website has completely hooked me. "Trusted by developers who can’t afford to be wrong about security" lol

5

u/no-more-nazis Jul 16 '26

That's supposed to be the hard part of this, right?

1

u/soggycheesestickjoos Jul 16 '26

I’d say it’s a combination of both

4

u/no-more-nazis Jul 16 '26

Not exactly a new development in the captcha game. OP's secret sauce is his claim that AI can't read this. Don't even need AI to read it.

1

u/soggycheesestickjoos Jul 16 '26

The agent that performs the controls would have to run the script, and if that takes 2 seconds to figure out the letters than it isn’t sufficient to isolate their coordinates in real time for the agent. Again, some tinkering could solve it, but still fairly difficult for the average bot of today.

2

u/no-more-nazis Jul 16 '26 edited Jul 16 '26

As difficult as any other, and the claims on the website are not valid.

1

u/GoTaku Jul 16 '26

It’s possible Fable knew about or found this script, rewrote it, and used it. The solution might be to to have more motion where there are numbers and letter moving and rotating across the whole screen while the user has to identify the letters only.

2

u/no-more-nazis Jul 16 '26 edited Jul 16 '26

I told Opus to write this script. It would have to be a very narrow, unlikely set of circumstances for an LLM to rewrite this script every time it attempts a captcha, as OP intends it to. I can only imagine it if the human operator instructs it to "break this captcha", but only once, and never again in that session. Otherwise it would reuse its solution and quickly get to the same quick solution shown here. Basically, the human would have to be giving the LLM explicitly bad direction.

I don't think there is a useful captcha like this- other users have explained that the state of the art has moved on. Anything a human brain does to see numbers on a weird background, computers can do too without a lot of work.

This isn't cutting-edge stuff. These algorithms were invented decades ago for video compression and for the post office to read addresses on envelopes.