If you have URL’s that contain a weird hashed query string starting with ?SID=, than you have enabled a security setting in your Magento configuration.
What is the purpose of SID?
If you have multiple stores on one domain and want to keep your users logged in, than enabling this setting keeps the user logged in.
Where can I change this setting?
- Login to your Magento admin Panel
- Hover over Settings
- Click on Configuration
- In the right hand sidebar menu click on Web
- Click on Session Validation Settings
- Here you can toggle the feature on and off.