Meltdown and Spectre are two major computer vulnerabilities in the news these days. A fairly descriptive
article explains that an attacker could gain access to your system through your web browser.
To protect yourself, make sure you are using the latest version of Chrome or Firefox as your browser, and keep your operating system updated with the latest patches.
Meltdown is an even more serious problem, in that it requires a new CPU, and reportedly affects only Intel chips. So maybe, if you're looking to buy a new intel device, you might want to consider AMD or waiting. Unfortunately, the "fixed" chips will run 5%-50% slower (although 30% gets most widely reported).
Apparently the CEO of Intel knew of the vulnerability before he started selling off his stock in the company, and this was a factor causing Google Project Zero to reveal the issue.