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An external image showing your user-agent and the total "hit count"

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[–] [S] 200 points 3 years ago (11 children)

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.

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  • [–] 59 points 3 years ago (1 child)

    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 :-)

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  • [–] 17 points 3 years ago* (1 child)

    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)

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  • [–] 36 points 3 years ago* (3 children)

    None (by Lemmy), as Lemmy doesn't actually request the image (that would be proxying). Your browser requests the image directly by URL. Lemmy, technically, doesn't even know an image exists. It just provides the HTML and lets your browser do the work.

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  • [–] 17 points 3 years ago* (2 children)

    Exactly. The text of this post is simply :

    ![An external image showing your user-agent and the total "hit count"](https://trilinder.pythonanywhere.com/image.jpg)
    I get the same result when I browse directly to the link.

    So, if OP links a malcious website we have a problem ... (?).

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  • [–] 10 points 3 years ago (1 child)

    Oh dangit, it's simpler than I thought. So the only data being sent is...just whatever is sent in your average GET request.

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  • [–] 24 points 3 years ago* (last edited 3 years ago) (4 children)

    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.

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  • [–] 17 points 3 years ago

    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.

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    [–] 171 points 3 years ago* (last edited 2 years ago) (39 children)

    [This comment has been deleted by an automated system]

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    [–] 56 points 3 years ago (2 children)

    Oh neat, Jerboa doesn't identify itself. Cool.

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  • [–] 55 points 3 years ago* (1 child)

    I'm fine with this. Instances shouldn't proxy or cache images because it opens instance owners to a lot more liability than text. A client side setting to not load images in comments by default is better.

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    [+] 51 points 3 years ago* (last edited 1 year ago) (5 children)
  • [–] 34 points 3 years ago (3 children)
    • Jerboa - also just sees a Mobile Client
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    [–] 37 points 3 years ago (2 children)

    What is it supposed to say?

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  • [–] 34 points 3 years ago (2 children)

    Salient demonstration, but if image proxying were to come to Lemmy I'd hope it was made optional, as it could overburden smaller instances, especially one-person instances (like mine). We also need a simple integrated way of configuring object storage.

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    [–] 19 points 3 years ago*

    Easiest way to stop this from happening is to use ublock origin to block all third party request on your instance.

    One way to do this is via dynamic filtering. This is for advanced users so be sure to read the info page: https://github.com/gorhill/uBlock/wiki/Dynamic-filtering

    (Consider backing up your ublock settings before doing this)

    If you are using lemmy.ml your rule would be this:

    lemmy.ml * 3p block
    

    if you're using another instance then change the domain or use both rules cause you might end up visiting the others as well. Note that adding this rule wont work unless enable advanced features in ublock origin.

    EDIT: THIS MIGHT BREAK THINGS ON YOUR INSTANCE, its recommended to learn how to use dynamic filtering to unbreak it: https://github.com/gorhill/uBlock/wiki/Dynamic-filtering:-quick-guide If it breaks stuff just remove that rule.

    You could also block it using static filters but I can't remember how to do that exactly, if you know please reply below.

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  • [–] 16 points 3 years ago

    VPN using Librewolf user checking in. This post got nothing on me.

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  • [–] 16 points 3 years ago (4 children)

    I'll be damned. I tried this from three different platforms and you've nailed it.

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    [–] 15 points 3 years ago (1 child)
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    [+] 14 points 3 years ago* (last edited 2 years ago) (4 children)
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    [–] 14 points 3 years ago

    I would've hoped that lemmy users on a c called privacy would understand the technology better, but I guess not.

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  • [–] 13 points 3 years ago

    What does it say? on jerboa is states that i use unknown mobile client, with infinity, android client. All i have is adaway on my phone

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  • [–] 12 points 3 years ago (2 children)

    for a little extra creepiness, modify the image-generating script to add geoip location data and http referer to the image.

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    [–] 11 points 3 years ago

    Man, I remember I scared the crap out of trolls on Reddit when we started arguing over DM, and I added a link to a meme that tracked their IP and system info (without them knowing ofc). Let's just say they went AFK quickly after that. Good times!

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  • [–] 10 points 3 years ago (7 children)
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    [–] 10 points 3 years ago* (last edited 3 years ago) (3 children)

    Even without instance proxy, it should easy enough on the client side to not pull remote images unless directed to do so, similar to most email clients these days. At least it gives people a warning that they're passing data to a 3rd party location.

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