The latest Firefox 51 beta version has added a DNS leak detection feature that will warn you if your Internet service provider is leaking DNS information.
According to the developer notes, Firefox 51 Beta 6 contains a DNS “leak” test which will warn users if they are leaking DNS data.
The test is enabled by default and can be enabled by going to Options -> Options -> DNS Leak test.
When enabled, the leak test will warn if your DNS service provider has leaked information that may be harmful to the health of your computer.
A notification will appear to say “This DNS leak is harmful to your computer.”
When the leak is detected, the notification will also say “You are using a service that can leak DNS information.”
In the case of a DNS server that is leaking information about your network or network access, Firefox will warn your browser that the leak may be malicious.
The leak test is an important addition to Firefox because it’s been known to cause some people to experience a decrease in online privacy, according to security researcher Tim Hunt.
The test will be enabled in Firefox 56 and in Firefox 57.
Hunt has not found any problems with the leak in Firefox 61 or Firefox 62, although Firefox 63 will include the DNS test.
In the meantime, you can check your DNS settings by going into your Firefox Settings.
The notification will warn that you may be leaking DNS settings.