The Long Term Service Release (LTSR) program for XenApp and XenDesktop 7.6 provides stability and long-term support for the XenApp/XenDesktop 7.6 release.
The latest update to LTSR is Cumulative Update 4 (CU4). Citrix recommends that you update the LTSR components of your deployment to CU4.
If you are new to the LTSR program and did not deploy the original XenApp/XenDesktop 7.6 LTSR release, there is no need for you to install it now. Instead, Citrix recommends that you bypass the 7.6 LTSR release and begin right with CU4. Documentation of the entire 7.6 LTSR release is available here.
In addition, Citrix also recommends specific versions of Citrix Receiver and other components. While not required for LTSR compliance, upgrading to the current versions of those components ensures further ease of maintenance and the availability of the latest fixes in your deployment.