Why you’re seeing a security alert about an “rnd” file

In some instances, security plugins such as WordFence may generate a warning similar to the following:

Unknown file in WordPress core: wp-admin/.rnd

What is this file and is it a threat?

UpdraftPlus uses the .rnd file to generate random numbers and perform certain encryption tasks. It’s harmless and will be recreated automatically if deleted.

What should I do?

You can either ignore the warning or adjust your security plugin settings to recognise the file.