I have more karma, and I wonder where are the hacked websites as well.

That's cool, I can answer this more kindly then.

If you're looking for obvious site defacements, something loudly compromised... that's usually not the game here. What is more likely is persistent covert shell access, hiding underneath. Accessible only to those who know the way in, doesn't draw attention to itself so it can persist for a long time before being used... a bit like the 11 month old account you've referenced here, that gets used to comment on this thread.

Sites with shell access become useful as part of botnets, for DDoS attacks. Setting up VPNs to provide lateral movement across to other websites. Why blow your cover by announcing your presence? A lot more damage is done in stealth.

I'm not in cybersecurity, but if you hunt around you'll find enough info about sites getting caught up in this.

Because clearly when you hack and rootkit a box, the first thing you do is announce it to the public

The exploit requires OOM, no? Half-decent observability should detect it easily.