This is possible because Lemmy doesn’t proxy external images but instead loads them directly. While not all that bad, this could be used for Spy pixels by nefarious posters and commenters.
Note, that the only thing that I willingly log is the “hit count” visible in the image, and I have no intention to misuse the data.
I think proxying everything through lemmy would have a pretty big bandwidth/scalability impact. I expect the lemmy clients dont send any unique user info on these image requests so not sure how useful it would be as a spy pixel? Maybe I’m missing something :-)
It would be interesting to see just how much info is shared when lemmy requests the image. If there is [potentially] sensitive info being shared, the devs might be interested in working on it too (I have no idea how to check such a thing, this comment is just so I can find the post later when more people have shared their wisdom on it)
Notably, this allows remote parties to associate your IP address with your interests, as revealed by the Lemmy communities that you browse.
One way is for the image host to use the HTTP Referer field. (Standards-respecting web browsers pass the URL of the web page being viewed to the server hosting the image.)
Another way is by posting an image with a unique URL.
Even if Referer is withheld and the image is not unique, the image host can still do basic fingerprinting of your client’s request header and your OS’s TCP quirks, and associate that fingerprint with your IP address.
An option for Lemmy to proxy media would be very helpful. Small instances could perhaps disable it, although they might not need to, since the additional load would scale with the number of users on that instance.
Were you expecting otherwise? Loading an external image is no different than loading an external website with images. Lemmy and reddit are link aggregators, not proxies. Having to proxy everything would run a significant bandwidth for instance admin who are often paying out of pocket for hosting.
It’s just a simple Flask server. I parse the user-agent using the user_agentsPython library, apply some conditionals upon the result, render the image using Pillow and send it to the user.
This is possible because Lemmy doesn’t proxy external images but instead loads them directly. While not all that bad, this could be used for Spy pixels by nefarious posters and commenters.
Note, that the only thing that I willingly log is the “hit count” visible in the image, and I have no intention to misuse the data.
Nice example!
I think proxying everything through lemmy would have a pretty big bandwidth/scalability impact. I expect the lemmy clients dont send any unique user info on these image requests so not sure how useful it would be as a spy pixel? Maybe I’m missing something :-)
It would be interesting to see just how much info is shared when lemmy requests the image. If there is [potentially] sensitive info being shared, the devs might be interested in working on it too (I have no idea how to check such a thing, this comment is just so I can find the post later when more people have shared their wisdom on it)
Notably, this allows remote parties to associate your IP address with your interests, as revealed by the Lemmy communities that you browse.
One way is for the image host to use the HTTP Referer field. (Standards-respecting web browsers pass the URL of the web page being viewed to the server hosting the image.)
Another way is by posting an image with a unique URL.
Even if Referer is withheld and the image is not unique, the image host can still do basic fingerprinting of your client’s request header and your OS’s TCP quirks, and associate that fingerprint with your IP address.
An option for Lemmy to proxy media would be very helpful. Small instances could perhaps disable it, although they might not need to, since the additional load would scale with the number of users on that instance.
Were you expecting otherwise? Loading an external image is no different than loading an external website with images. Lemmy and reddit are link aggregators, not proxies. Having to proxy everything would run a significant bandwidth for instance admin who are often paying out of pocket for hosting.
How do you get an image to run code? I guess I somehow missed something important in website development.
Edit: I saw that you said you’re using Pillow to actually render the image from code. That’s neat! …and scary
deleted by creator
Share source code? I’m curious
It’s just a simple Flask server. I parse the user-agent using the
user_agentsPython library, apply some conditionals upon the result, render the image using Pillow and send it to the user.