Contractor payment issues with publicly traded companies is a protected class?

This is about as broad and vague as a question can get, so the only way to answer it is to say that an employee can fall into a "protected" classification, if they blow the whistle on activity they reasonably believe to be a violation of statute or any other fundamental law of public interest. Whistleblowers can be internal or external.

I agree with Attorney Kirschbaum that an employee can fall within a "protected" class, but there isn't enough information here to give you a response.

It's difficult to interpret your question, but I'll give it my best shot. It sounds like you're asking whether complaining within the company about (over)payments to outside contractors/vendors can qualify for anti-retaliation protection. Typically, no, because so-called "whistle-blower" complaints require a complaint to an external government agency to be protected activity. There are some exceptions to this, but they are limited and fact-specific. I would therefore encourage you to contact a local employment law attorney directly to discuss the details of your particular case and determine your rights and options. I wish you luck.