Mendix 8.12.0 included a change that allows to strip invalid characters from XML* exported through OData, however the same kind of problem is still present when exporting arbitrary strings into XML via a regular XML export mapping.
Particularly the vertical tab character (ASCII 0xb) is unfortunately used in Microsoft Office documents, so it is easy to slide into values that are either copy&pasted from MS Office documents or imported from Excel files.
The idea is to extend the same option to replace invalid characters by DEL that was introduced for OData to all XML Export mappings.
(*) “We added a feature that allows for exporting invalid characters in published OData services. It replaces characters that are invalid in XML with the DEL character. (Ticket 101056)”