Not trying to be alarmist here, but perhaps time to talk about this topic too.
This is a mighty curious post (see in picrel too):
https://endchan.org/agatha2/res/166425.html#166607
I don't know how real this is. The implications are someone is trying to de-anonymize users. Seems like he gained access to the filesystem.

To give an idea with broad strokes. In theory this could happen if a malware fit for purpose is passed to the target's system, then it is executed, then the attacker can access the target host/machine.
Usually the malware has to be executable, but it is possible to add a "payload" to media files, and depending on OS and the program that opens it it can get executed.
How to "get" such malware? By downloading files of course.
Please be careful what you download. From here or from other places, eg. social media, direct messaging apps (discord) and file sharing services.
Keep your software up to date.
Run malware scans.
Open files in virtual environments, virtual machines or with containerization or in sandboxes.