Encryption keys that were generated in System > Manage Encryption Key were very weak; an attacker could easily recover them if he/she could access encrypted content. Encryption keys generated during installation are strong.
Part of patch MAGENTO 2.0.4 SECURITY UPDATE
This vulnerability affects the following application versions:
- Magento 2.0.0
- Magento 2.0.0-rc
- Magento 2.0.0-rc2
- Magento 2.0.1
- Magento 2.0.2