I am using Tor in Tails. To verify that I am connected correctly, I go to IP-check.info. Lately, IP-check.info is giving me a warning message "..you are not using Tor correctly. Your own IP address was uncovered as you do not enforce anonymity for all web addressees." This was preceded with a initial warning that my proxy settings are wrong. I did not change anything from the time that I was not getting this warning to now. However, I did notice some new behavior in the network settings of Tails. When I first connect to wifi in Tails, before I execute Tor, an additional "wired" connection appears in the settings windows showing a device with a different mac address. It doesn't appear to be active, and it way have nothing to do with the warning I'm getting. Your input and direction is appreciated. Thank you.
This sounds like a false negative.
ip-check.info (or any similar site) doesn't know "your own IP", it can detect that a different IP was used and assume it was a "leak", but this could just mean that your circuit broke mid-use and a new one was built in it's place, resulting in a new/different IP address.
These tests are fragile, even https://check.torproject.org/ is subject to false-negatives (I.E. it can occasionally incorrectly report you are not using Tor when you are).
I can't reproduce this issue from Tails 2.4.
Double-check your warnings, feel free to post them. And - there's a need to check your Tor console output. Is it working OK? You can post it here, so I'll be able to help you further, but basically Tails is not vulnerable in the way you've mentioned.