On the 23rd February 2016, Magento released an update for their Jan 20th 2016 security patch, SUPEE 7405.
These updates added support for PHP 5.3 and address issues with upload file permissions, merging carts and SOAP APIs which were experienced with the initial release in January. Magento made very clear that this update did not address any new security issues.
Magento have advised that if you are running Enterprise Edition prior to version 184.108.40.206 OR Community Edition prior to version 220.127.116.11 – you MUST install SUPEE 7405 v1.0 before installing SUPEE 7405 v1.1.
If you are running a later version, or have already installed v1.0 on an earlier version – you do not need to install v1.0 before installing v1.1.
We strongly advise that if you are not a developer / highly experienced with Magento development, that you request an experienced Magento developer or agency to apply this update for you.
Please see below for details regarding the contents of the patch bundle: (taken from the Magento website)
Cart Merge Patch (SUPEE-7978)
Carts with identical items now merge correctly. Previously, when a cart with one item was merged with another cart that contained the same item, Magento did not merge the cart totals correctly. The cart now includes only one item, and the total is correct.
SOAP API Patch (SUPEE-7822)
The Magento SOAP API now works as expected. Previously after installing the SUPEE-7405 v1.0 patch, an API request would cause a 500 error, and Magento would log an exception.
PHP 5.3 Compatibility (SUPEE-7882)
The patch was not compatible with PHP 5.3 for earlier versions of Magento that were still supporting this version. Merchants experiencing this issue were unable to view sales information in the Admin.
Upload File Permissions
The patch restores less restrictive file permissions (0666 for files and 0777 for directories) as more strict permissions introduced by the original SUPEE-7405 patch caused many merchants not to be able to view uploaded product images, depending on hosting provider configuration.