Who’s selling auto registration data–inspection place, Harris County, DPS, or something else?

Within a week of registering my car in Texas for the first time, I started getting a swarm of quasi-official looking "warning, your warranty on your (year) (model) is ending, call before it's too late" cards and letters in the mail.

Until I started the process of registering the car with Harris County, there was no information anywhere linking that car to my Houston address. The only organizations that have the information are the place that inspected the car; Harris County for auto registration; and DPS because I showed the registration receipt when I traded in my out-of-state license for a Texas license a few days later.

Is this information in public records? Is one of those organizations selling the data? TIA for any light you can shed.