security problem with who can see files?

We work with people with who we share certain files, and one of them told us they could see every file in our BOX account instead of just the one file we shared a link with.  We have two admins: the owner and I.  This is something that has to be corrected for sure.  Funny, when we re-sent the link, it worked just for the one file like it should have.  Please have someone contact me on this ASAP.