Tech firms are working to fix two major bugs in computer chips that could allow hackers to steal sensitive data.
Google researchers said one of the "serious security flaws", dubbed "Spectre", was found in chips made by Intel, AMD and ARM.
The other, known as "Meltdown" affects Intel-made chips alone.
The industry has been aware of the problem for months and hoped to solve it before details were made public.
The UK's National Cyber Security Centre (NCSC) said there was no evidence that the vulnerability had been exploited.
According to the researchers who found the bugs, chips dating as far back as 1995 have been affected.
Some fixes, in the form of software updates, have been introduced or will be available in the next few days, said Intel, which provides chips to about 80% of desktop computers and 90% of laptops worldwide.
Microchips are the basic electronic systems behind many devices such as computers and mobile phones.
In order to do their work, they must move data around, using different types of memory to temporarily store it.
In many cases, that information is supposed to be secure from attempts to snoop on it, but these two bugs mean that it could in fact be accessed by a third party.
The first reports suggested that a bug affected solely chips made by Intel, but it has since emerged that a separate flaw, Spectre, has been found in Intel, ARM and AMD chips.
"Many types of computing devices - with many different vendors' processors and operating systems - are susceptible to these exploits," said Intel.
ARM said patches had already been shared with its customers, which include many smartphone manufacturers.
AMD said it believed there was "near zero risk to AMD products at this time".