Let PHP handle the session garbage collection to have the same behaviour as file based sessions regarding session life time
Don't accept GET and POST session IDs if SESSION_FORCE_COOKIE_USE is true
Only set the session_id if it differs to the cookie value (session_id($id) always sends a cookie in session_start() and SID is always set, so we do this only when needed)
If SESSION_FORCE_COOKIE_USE is enabled and the first request is made to login.php, no cookie is found (but is set) so perform another check before redirecting directly to the cookie_usage.php page
Block orders where the shipping address does not match a defined shipping module zone
Bugfix: Double Query

Remove double query, thanks to Matt @mattjt83
Remove check on nonexisting $free_shipping variable
Add message stack output to checkout confirmation page
Introduce certificate bundle for secure curl connections
If a module has been installed and the module files were deleted, the parameters would still exist in the database. If the module files were copied again to the modules directory, installing the module would introduce duplicate module parameters, so when installing a module, check if it has been installed previously and call its remove() function before installing the module again.
Force HTTPS on Admin when SSL is enabled
New Content Modules implementation for the Account, Checkout Success, and Login pages.
update version
Update Administration Tool Dashboard Latest News and Latest Add-Ons
modules
Place Orders link in own box
Introduce new Card Acceptance box
PayPal Modules:
Update PayPal Express Checkout payment module
Update PayPal Payments Standard payment module
Update PayPal Payments Pro (Direct Payments) payment module
Update PayPal Express Checkout (Payflow Edition) payment module
Update PayPal Payments Pro (Payflow Edition) payment module
Introduce PayPal Payments Pro (Hosted Solution) payment module
Introduce Log In with PayPal content module
Sage Pay Modules:
Update Sage Pay Direct payment module
Update Sage Pay Form payment module
Update Sage Pay Server payment module
Introduce Sage Pay Cards Management Page content module
Authorize.net Modules:
Update Server Integration Method (SIM) payment module
Update Advanced Integration Method (AIM) payment module
Introduce Direct Post Method payment method
Stripe Modules:
Introduce Stripe.js payment module
Introduce Stripe Cards Management content module
Braintree Modules:
Introduce Braintree payment module
Introduce Braintree Cards Management Page content module
Update WorldPay Hosted Payment Pages payment module