Corel CCX is a vector graphics file format, used for example in the Corel Gallery 1 Million clip art collection. It is a compressed form of CMX (Corel Presentation Exchange).
See also Corel Gallery.
Some format lists say there is a CPX/.cpx format, described as "CMX compressed", but evidence is lacking.
Corel says that the Corel ArtShow 5 book+CD product used a CPX format. More research may be needed here.
CMX files start with "
RIFF", and have "
CDRX" at offset 8.