At Rand Marketing, we average installing over 100 Magento security patches per year. These include incremental patches for sites that we help to maintain in the long term and bulk patching for new clients that have fallen behind in updating their sites to avoid security threats.
In each instance, we work on a development copy of your site, testing to see how your instance of Magento reacts to new patches, adjusting as needed, and allowing you to test in a staging area to verify that the upgraded copy of your site works as intended.
Magento sites react differently to patches due to conflicts with various Magento Extensions, Themes, and Customizations. While we can't predict exactly how your site will react to a given patch, we can install patches for you, and based upon conflicts, provide estimates and recommendations to resolve any issues. If you need a patch that's known to be incompatible with many extensions, or cause other issues, we do our best to provide more specific estimates.