This bug relates to the behaviour of the ViewEngineResult.Render method in VS2013 under MVC 5 however the problem is also present if I load a previously working MVC 4 project into VS2013.
In VS2012 we could use ViewEngineResult.Render to render a MVC view to a string. This was useful for generating emails from a View or for returning raw html to the client to incorporate into the UI client side using JS.
Under VS2013 this method is returning html strings containing malformed tags. For example the following is returned if you attempt to render the About.cshml page from the pre-canned app generated when creating a new MVC application in VS2013.
<$A$> <hgroup> <h2></$A$><$B$>About</$B$><$C$>.</h2> <h3></$C$><$D$>Test page for Render View test</$D$><$E$></h3> </hgroup> <div</$E$><$F$> class="row-fluid"</$F$><$G$>> <div</$G$><$H$> class="span12"</$H$><$I$>> <p>Use this area to provide additional information.</p> </div> </div></$I$>
Note this is generated using the iis express webserver included with VS. i have not tried to deploy this to a full iis server yet so not sure if the issue lies with VS or IIS Express? I have a small test application to demonstrate the error if needed.