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A comment on Firefox 85 cracks down on supercookies. Parent comment

Re:Firefox 85 cracks down on supercookies by floatboth on Tuesday January 26, 2021 @01:07PM (#25919165)
With some forms of caching it's much simpler: the browser sends an ETag or If-Modified-Since and the server is supposed to return 304 Not Modified to optimize the load if the cached resource is still valid.
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Re:Firefox 85 cracks down on supercookies by kortilla on Tuesday January 26, 2021 @05:58PM (#25922032)
But from JavaScript I don’t think you can see that. You just get the end result of the image being served to you. You have to infer it from timing.
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Re:Firefox 85 cracks down on supercookies by megous on Tuesday January 26, 2021 @07:13PM (#25922619)
https://megous.com/dl/tmp/705dc9a2477d1f95.png

For cross-origin, you'd add CORS.

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