KRACK attacks: breaking WPA2krackattacks.com
Two Belgian researchers (jeej Belgium) have been able to break the Wifi encryption standard WPA2. Depending on the specifics of each implementation, they can listen in on traffic, catch credentials or change website content. Pretty much all wifi enabled devices will need to be updated.
The link above points to the website of the researchers, providing a great explanation. This post gives a good pragmatic overview of the consequences.