Citric acid is a common food additive. You’ll frequently find it in fizzy drinks or in places where high acidic fruits would be found. It was historically derived from acidic fruits, like lemons or limes. Citric acid is currently produced microbially, that is, chemically with sugars. Most citric acid producers begin with corn-based sugars.
To date, I have not heard of or seen any instance of a non-vegan produced citric acid.