It is very, very rare to be randomly placed into a modded lobby. Modders seek to make money and hid their activities.
- Do not accept an invite from people you do not know.
- If you see everyone moving too fast, scores too high, etc. Dashboard right away.
In more than 120 days of play across various COD titles I have been placed in exactly one modded lobby. You won't be in trouble for finding a single game and backing out.