Shopware is an open source e-commerce software. The mail validation in the registration process had some flaws, so it was possible to construct different mail addresses, that in the end result in the same address, which is shared by multiple accounts. This issue has been addressed in version 5.7.18 and users are advised to update. There are no known workarounds for this vulnerability.
The product does not check or incorrectly checks for unusual or exceptional conditions that are not expected to occur frequently during day to day operation of the product.