Employers gossiping to other companies...this can't be legal

After being fired from Logans Roadhouse I found out that my previous employer had told a manager at another company about a video I had made that was posted online by an ex. Originally I told my GM about the situation because I was being harassed at work by team members ( which he did nothing about ). The whole thing escalated which resulted in me getting terminated. After I was fired I found out that a manager I did not tell had told someone at a different company I was planning on applying to. Because of this I fear that I'll be discriminated against. Black balling? Slander? Either way I KNOW this isn't legal