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What are these comments on lemmy posts? (lemmy.sdf.org)

submitted 1 year ago by Fleecer74@lemmy.sdf.org to c/asklemmy@lemmy.ml

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Are they just an issue with wefwef or trying to use an exploit

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[-] Xylight@lemmy.xylight.dev 9 points 1 year ago

Doesn't Lemmy use HttpOnly cookies? This would fix any js based exploit.

[-] Dirk@lemmy.ml 4 points 1 year ago

Also, strict CSP would prevent it entirely.

[-] Xylight@lemmy.xylight.dev 0 points 1 year ago

out of curiosity, what CSP options would fix this?

[-] Dirk@lemmy.ml 5 points 1 year ago

To prevent execution of scripts not referenced with the correct nonce:

script-src 'self' 'nonce-$RANDOM'

To make it super strict, this set could be used:

default-src 'self';
script-src 'nonce-$RANDOM'
object-src 'none';
base-uri 'none';
form-action 'none';
frame-ancestors 'none';
frame-src 'none';
require-trusted-types-for 'script'

Especially the last one might cause the most work, because the "modern web development environment" simply cannot provide this. Also: form-action 'none'; should be validated. It should be set to self if forms are actually used to send data to the server and not handled by Javascript.

The MDN has a good overview: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy

[-] Tartas1995@discuss.tchncs.de 2 points 1 year ago

I don't know what Lemmy uses tbh. I don't even know if the code would work when run. Like i don't know e.g. if they grab the username(?) correctly. I just understand their intentions but yeah their execution might be horrible.

[-] erre@feddit.win 0 points 1 year ago

I'd be willing to bet they're using the API to make all the changes. The cookie has the jwt token. I don't believe you need the username (at least judging by the js API docs).

this post was submitted on 10 Jul 2023

135 points (97.2% liked)

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