Back in June 2017, I came across this article which talks about VPN leak. So what exactly is a VPN leak?
Quote: "When you're running a VPN, the expectation is that all the traffic sent and received over the VPN encrypted tunnel is protected. That includes info like your IP address, your location, even what internet service provider you're using. If that information is knowable, then tracking your online behavior isn't far behind. If you're lucky, all that happens is your web activity is monetized. But that's not always the case."
Today, I read another article which shows more about VPN leaks and the number of VPN service providers which actually leak your ip.
Source: https://voidsec.com/vpn-leak/
You can check if your VPN leaks visiting: https://ip.voidsec.com/
Something I'm not sure about if this is applicable to proxies. (I don't use them, maybe someone who uses them can do a quick check)