The Mirai botnet is exploiting a command injection vulnerability found in certain discontinued D-Link routers. This issue emerged about a year after the vulnerability was publicly disclosed and proof-of-concept exploit code was released. Users of these routers are at risk, as the botnet can take control of the devices, potentially turning them into part of a larger network for launching attacks. The fact that these routers are no longer supported by D-Link means that affected users will not receive any official security updates or patches, leaving them vulnerable. It's crucial for individuals and organizations still using these routers to take immediate action to secure their networks, as the exploitation is ongoing.