Sitefinity 5.1 SP1 has just been released. This is a service release aiming to provide quality improvements over Sitefinity 5.1. Full list of Sitefinity 5.1 features and improvements can be seen here.
What's fixed:
User with Modify page permission can get "Object reference not set to an instance of an object." when trying to edit a page created by an Administrator
Kendo_common_min.css is not loaded when using custom backend theme in Sitefinity 5.1 - PITS
Issue with existing E-mail campaigns subscribers after upgrading from 4.x/5.0
Cannot perform upgrade when there are more than 2000 dynamic content items created, due to long SQL queries
API issue in modules inheriting from Content Module Base class
MVC case sensative URL resolving issue
Content life-cycle is broken when used in Bootstrapper.Initialized event.
Responsive design CSS is always constructed from the database and not cached (performance optimization)
Creating Search index for documents requires a page where these documents are published
"Unsupported language "en-US"" error in web page Email Campaigns after upgrade from 4.x/5.0
Membership provider with key 'OpenAccessMembership37Provider' cannot be added for module 'Migration' error after an upgrade
Tag selector in widgets does not keep selections when paging
Tags are not ordered alphabetically
There is no “type to narrow” filter box in the Tag Selector control
Wrong assembly in SearchResults widget template
JS error when selecting one particular item to be shown in the front-end for news, events and blog posts