Course Hero can at times be a helpful resource for students. Course Hero promotes itself as providing study resources, course notes, test prep, among other services to students. It sounds good in theory. The unfortunate reality of it is that colleges and universities often charge students for using online resources such as Course Hero.
Whether a student is in fact in the wrong for doing so will depend on the specific circumstances at hand. Did the professor or the school specifically prohibit the use of Course Hero? If so, then it's obviously an issue. If the school did not do so, it may be a more nuanced consideration. It is a serious allegation and you can not depend on the school to do the right thing. You have to take the necessary precautions. Having an experienced attorney-advisor will be your best ally to help you understand and navigate the process.