TOR web browser is excellent for hiding your actual IP address but a recent vulnerability exposes your real IP address to certain type of web pages. This vulnerability was discovered by an Italian security researcher, Filippo Cavallarin who said this is already an issue in Firefox which is what is used by TOR browser as well. For some reason, this issue is only faced by Mac and Linux users. Windows users need not worry about anything. Details of this flaw have not been revealed publicly.