Is my mining rig a security risk I need to worry about?

Yes, to a degree, because a mining rig is an ordinary computer that runs unattended for long periods, which makes it a target. The main risks are running unverified mining software that hides malware, and leaving the machine with weak remote access. Protect it by building on a clean, updated system, downloading miners only from official sources and verifying them, refusing pre-configured miners shared in chat groups, and keeping your wallet keys off the rig entirely. Mine to an address whose rewards you sweep to safer storage. Watch for dropped hash rate, unknown processes, and any changes to your payout address.