‘Meltdown’ and ‘Spectre’ are bugs that obtain information about areas of memory on your devices, that’s previously been unobtainable to attackers. It can include sensitive data, so find out how to protect yours, or your organisation’s devices against them.
National Cyber Security Centre advice
For business: https://www.ncsc.gov.uk/guidance/meltdown-and-spectre-guidance
For home: https://www.ncsc.gov.uk/guidance/home-user-guidance-manage-processor-vulnerabilities-meltdown-and-spectre