I mean seriously, 21H1???
In case you’re wondering, that name (21H1) is meant to make clear that the update was released in the first half of 2021. Earlier updates were given names like 1909, for the update released in or after September 2019 (though it wasn’t actually released until November). The H1 or H2 bit is, I think, to avoid tying the name to a particular month.
Well, it’s not totally inconceivable that viruses could spread through Windows updates.