Minecraft itself is stable and safe, but surrounding factors can cause issues if you're not careful.
Direct Risks
Resource Intensity: Heavy modpacks, high-res resource packs, or massive worlds can max out CPU, RAM, and GPU, leading to overheating on inadequate cooling.
Buggy Mods/Packs: Unofficial mods may contain memory leaks, crashes, or world corruption.
Indirect Risks
Malware: Downloading mods from shady sites can infect your system.
Disk Space: Massive worlds + backups can fill drives, slowing the OS.
Overheating: Long sessions on laptops or poorly ventilated desktops may throttle or damage components.