Hey, yeah, I wrote the article. This (of course) would be more practical. Thanks for pointing it out. I wanted the payload to "live" in actual pixel data rather than hidden text inside an XML file. That’s why I went this way :)
I'd imagine the (aggressive) caching of the favicon by browsers makes it a challenge, but you could generate the favicon dynamically, then have JS extract the sequentially. Basically streaming arbitraily large content to a webpage via favicons. Via blocks of 239 bytes.
It may be a fun, novel way to proxy webpages that are otherwise blocked. Though, i guess, the service rendering the favicons can just as easily be blocked then.
PNG has comment chunks tEXt, zTXt, and iTXt. You can have a completely normal image whose file is stuffed with as much content as you want. That is less fun, I suppose.
You can use the favicon cache as storage too, by redirecting users across domains. It's been proposed as a potential fingerprinting risk[0], and if a browser naively reuses the cache for incognito mode, it could be used to track users across browser profiles.
for the first time in a while on HN, i disagree with the characterisation as AI-generated. at most it was drafted with an LLM, but the final output is pretty human to me.
they used the wrong it’s/its, made But. its own one-word sentence, didn’t capitalise HTML, and used “okayy” in parenthesis. all of this isn’t to criticise the writer - i enjoyed it more seeing these little imperfections that make up a blog post
Yeah, but it's kinda weird. The typical LLM headers and bullet points are there, but it's like someone took an axe to the rest of the spew. I too would rather read someone's original bad writing than their bad editing of AI writing, but it's kinda interesting how this all shakes out.
I guess the decoder is more than the 208 bytes that this page uses..
But maybe you can misuse this and store a session ID / cookie in a favicon (give everyone a unique one) and survive some cookie cleanup and evade privacy restrictions?
Maybe you can still make it that the favicon looks like an image a little to not raise suspicion?
Favicons seem to be cached across private browsing sessions. Oh no
Love it. Did you see the old effort to store the page in the url? https://github.com/jstrieb/urlpages
Instead of going via pixels, why not use a SVG favicon and directly store markup inside it and extract it?
Use this favicon.svg:
use this in your <head> to use a svg favicon: finally, use this in your <body> to extract it and add it to your document body:An SVG can embed raster images: base64 encoded bytes.
So you could layer this experiment: favicon is svg, that contains encoded raster, whose bytes are encoded html.
At the very least it would make a mindboggling CTF step.
Hey, yeah, I wrote the article. This (of course) would be more practical. Thanks for pointing it out. I wanted the payload to "live" in actual pixel data rather than hidden text inside an XML file. That’s why I went this way :)
The ico file format allows multiple resolution icons, so a lot of data
Good point, I might add a section in the article where I list alternative approaches. Thanks
I'd imagine the (aggressive) caching of the favicon by browsers makes it a challenge, but you could generate the favicon dynamically, then have JS extract the sequentially. Basically streaming arbitraily large content to a webpage via favicons. Via blocks of 239 bytes.
It may be a fun, novel way to proxy webpages that are otherwise blocked. Though, i guess, the service rendering the favicons can just as easily be blocked then.
PNG has comment chunks tEXt, zTXt, and iTXt. You can have a completely normal image whose file is stuffed with as much content as you want. That is less fun, I suppose.
Yes, that would also work, thanks for pointing it out
You can use the favicon cache as storage too, by redirecting users across domains. It's been proposed as a potential fingerprinting risk[0], and if a browser naively reuses the cache for incognito mode, it could be used to track users across browser profiles.
[0]: https://www.schneier.com/blog/archives/2021/02/browser-track...
Wasn't this fixed or mostly fixed?
Is this timing coincidence? I just submitted 1h (30 mins before this) ago a website I just made about storing your stock porfolio in a URL + favicon!
https://news.ycombinator.com/item?id=48606396
I found the agressively staccato, clearly LLM-generated content extremely difficult to read.
for the first time in a while on HN, i disagree with the characterisation as AI-generated. at most it was drafted with an LLM, but the final output is pretty human to me.
they used the wrong it’s/its, made But. its own one-word sentence, didn’t capitalise HTML, and used “okayy” in parenthesis. all of this isn’t to criticise the writer - i enjoyed it more seeing these little imperfections that make up a blog post
It’s the new internet. So, so annoying.
Which bit? The short sentences?
Yeah, but it's kinda weird. The typical LLM headers and bullet points are there, but it's like someone took an axe to the rest of the spew. I too would rather read someone's original bad writing than their bad editing of AI writing, but it's kinda interesting how this all shakes out.
I wish people would include their prompts.
Honestly it didn't interest me, but I do remember from back in the days full websites rendered by a browser from... Empty files. https://mathiasbynens.be/notes/css-without-html
I would have used a minimal service worker to unpack the web data and present it as if it were just a normal page being loaded.
Is it cake? Game for devs.
Pretty cool tbh!!! Would have loved seeing the decoder code!!!
It's also pretty interesting to think how an attacker could exploit images on his behalf. Never thought that would be a way!!!
Thanks!
I guess the decoder is more than the 208 bytes that this page uses..
But maybe you can misuse this and store a session ID / cookie in a favicon (give everyone a unique one) and survive some cookie cleanup and evade privacy restrictions?
Maybe you can still make it that the favicon looks like an image a little to not raise suspicion?
Favicons seem to be cached across private browsing sessions. Oh no
Very cool. I wonder is it possible to make a simple game with also leveraging the webassembly?
Yes, probably. I guess, you’d need a bigger favicon since the minimal Rust WASM binary is around 20KB+ (?)
You might find my tinkering useful: https://strich.io/blog/posts/embedding-webassembly-in-qrcode... A QR code isn’t much different from a favicon I guess. :)
The link is 404
Fascinating concept! Thanks for sharing this!
Would have been more fun if the blogpost was rendered from the favicon.
very cool and interesting after reading just the title I wrongly assumed this would be about svg
Surprised that a minimal "website" only requires a small image = few pixels = few bytes to store it? Um, ok.
Amazing!