I was at the grocery store just now to get some items. Although Cheez Whiz is not a product I use, I read the labels on the regular and light versions.
I am in Canada, and based on a read of the labels, they are both gluten-free per Canadian label regulations.
Both list mustard as an ingredient. Both say "Contains: Milk, Mustard"
The inclusion of mustard means they have been updated to comply with new rules effective August 4, 2012. Those revisions add mustard, and ALL GLUTEN GRAINS to the priority allergen list (wheat has been there for years).
FWIW, the ingredients did not list spices, but did list seasoning. Under the old rules, barley malt could conceivably have been hidden there, although I never found a case where it was.
I am a super sensitive Celiac and have recently tried Cheez Wiz in Canada, and I was fine. I have reacted to many other products
listed as gluten free by the manufacturer which were under 20 ppm such as Frenchs Mustard (I am currently having a severe reaction to Frenchs Yellow Mustard) but Cheez Wiz has not caused me any grief. Hooray!!