On Wednesday, a group of security experts revealed two security flaws that affect nearly all microprocessors, the digital brains of the world’s computers. These flaws, called Meltdown and Spectre, could allow hackers to lift passwords, photos, documents and other data from smartphones, PCs and the cloud computing services that many businesses rely on.

Some of the world’s largest tech companies have been working on fixes for these problems. But the researchers who discovered the flaws said one of them, Spectre, is not completely fixable. “It is a fundamental flaw in the way processors have been built over the last decades,” said Paul Kocher, one of the researchers who discovered these flaws.

Here is a guide to what you need to know and what you should do.

Where exactly are these flaws?

Both are issues with the way computer chips are designed.

Meltdown affects most processors made by Intel, the company that supplies the chips for a majority of PCs and more than 90 percent of computer servers.