How to avoid control group contamination?

When running a sociological experiment where subjects are randomly assigned to treatment and control groups and only the treatment group will be sent some information regularly (for example, weekly), how can the researcher minimize the risk of contamination of the control group (for example, if someone from the treatment group posts their information on social media or the like where anyone from the control group might see it)?

Is there any way (other than informing both groups of the importance of a control group) to reduce this risk of control group contamination?