Tested using 10.0.4.
If you use a plus character in a Product Reference (which seems to be allowed), the item can be successfully added to Cart and Checked Out.
However if you view the Cart and click on the link back to the product (the underlined name in the Cart) then you are sent to an error bounce page.
I.e. Using product reference "6+4":
The + sign is being erroneously replaced by a space.
The obvious workaround is to not use plus signs in your product references but the real fix would need Perl changes.
P.S. To verify this I created another product with reference "6 4" and sure enough the Cart erroneously links back to that instead of the proper product.
If you use a plus character in a Product Reference (which seems to be allowed), the item can be successfully added to Cart and Checked Out.
However if you view the Cart and click on the link back to the product (the underlined name in the Cart) then you are sent to an error bounce page.
I.e. Using product reference "6+4":
The specified product reference (6 4) couldn't be found.
The obvious workaround is to not use plus signs in your product references but the real fix would need Perl changes.
P.S. To verify this I created another product with reference "6 4" and sure enough the Cart erroneously links back to that instead of the proper product.