org-export-filter-plain-text-functions is a variable defined in `ox.el'.
Its value is
nil
This variable may be risky if used as a file-local variable.
Documentation:
List of functions applied to plain text.
Each filter is called with three arguments: a string which
contains no Org syntax, the back-end, as a symbol, and the
communication channel, as a plist. It must return a string or
nil.