from Hacker News

Recently I bought a used iPhone for my daughter. After a factory reset, I went into its settings and noticed it still has an MDM certificate installed from the previous owner. For whatever reason, I am having difficulty removing this certificate and I would like to know if leaving this certificate on this iPhone would pose any danger, such as a remote takeover or leaking any of my daughter's information either to the original owner or a third party.

Is leaving an unknown MDM certificate from the previous owner on an iPhone a security risk? If so what is the best way to remove it?