As others have pointed out, that's a weak way to attach anything to
stucco. After all, it's at best about 1/2" thick. Just use screws
long enough to bite into the wall sheathing (plywood or 3/4"
boards).

Unfortunately that only works if there is OSB or plywood as sheathing. In
a
non-stress location, it could likely be fiberboard behind the stucco that
won't
hold a screw.

Fiberboard as wall sheathing? Really? Sounds kinda flimsy.

Never seen it but I'll take your word for it if you say so.



*It is flimsy. One big condo/townhouse development that I do work in has
that under the vinyl siding. It is only 3/8" or 1/2" thick and has a foil
backing and no other underlayment behind it. When I do an outdoor
receptacle I have to be sure that I am next to or over a stud so that I have
something solid to screw into.