The vulnerability stems from improper validation of serialized data during order processing. PrestaShop's protection mechanism checked for '0:' followed by digits but missed '0:+' patterns. This suggests a regex-based validation in a deserialization helper function (like Tools::unSerialize) was bypassed. The Tools class is a common location for serialization utilities in PrestaShop, and the patched version 1.7.2.5 would have modified this validation logic. The high confidence comes from the attack pattern (PHP object injection via unserialize) and the documented bypass technique targeting serialization validation.