While "free" and "repack" versions are convenient, safety should be your top priority. Follow these guidelines:
Unlike a VPN, which requires software installation, a web proxy works directly in your browser. You just type the URL and go. Safety Tips for Using Free Web Proxies
A version of the site stripped of heavy ads or extra features for faster loading on slow connections. Key Features of the ProxySite Experience
If a repackaged site is covered in aggressive pop-ups, it may be hosting malicious scripts. Stick to well-known mirrors.
Never log into your bank account or enter credit card information while using a free web proxy. Even with encryption, the proxy provider (or the person who "repacked" the site) could theoretically see the data passing through.