Once you deploy your website into big rocks you are getting the /Security Error.,
I faced the similar issue like below
Security Exception
Description: The application attempted to perform an operation not allowed by the security policy. To grant this application the required permission please contact your system administrator or change the application's trust level in the configuration file.
Exception Details: System.Security.SecurityException: Request failed.
Source Error:
An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
Stack Trace:
[SecurityException: Request failed.]
System.Security.CodeAccessSecurityEngine.ThrowSecurityException(RuntimeAssembly asm, PermissionSet granted, PermissionSet refused, RuntimeMethodHandleInternal rmh, SecurityAction action, Object demand, IPermission permThatFailed) +165
System.Security.CodeAccessSecurityEngine.ThrowSecurityException(Object assemblyOrString, PermissionSet granted, PermissionSet refused, RuntimeMethodHandleInternal rmh, SecurityAction action, Object demand, IPermission permThatFailed) +100
System.Security.CodeAccessSecurityEngine.CheckSetHelper(PermissionSet grants, PermissionSet refused, PermissionSet demands, RuntimeMethodHandleInternal rmh, Object assemblyOrString, SecurityAction action, Boolean throwException) +272
System.Security.CodeAccessSecurityEngine.CheckSetHelper(CompressedStack cs, PermissionSet grants, PermissionSet refused, PermissionSet demands, RuntimeMethodHandleInternal rmh, RuntimeAssembly asm, SecurityAction action) +55
System.RuntimeTypeHandle.GetTypeByName(String name, Boolean throwOnError, Boolean ignoreCase, Boolean reflectionOnly, StackCrawlMarkHandle stackMark, IntPtr pPrivHostBinder, Boolean loadTypeFromPartialName, ObjectHandleOnStack type) +0
System.RuntimeTypeHandle.GetTypeByName(String name, Boolean throwOnError, Boolean ignoreCase, Boolean reflectionOnly, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean loadTypeFromPartialName) +70
System.RuntimeType.GetType(String typeName, Boolean throwOnError, Boolean ignoreCase, Boolean reflectionOnly, StackCrawlMark& stackMark) +39
System.Type.GetType(String typeName) +50
System.CodeDom.Compiler.CompilerInfo.get_IsCodeDomProviderTypeValid() +10
System.Web.Compilation.CompilationUtil.GetRecompilationHash(CompilationSection ps) +2090
System.Web.Configuration.CompilationSection.get_RecompilationHash() +107
System.Web.Compilation.BuildManager.CheckTopLevelFilesUpToDateInternal(Int64 cachedHash) +465
System.Web.Compilation.BuildManager.CheckTopLevelFilesUpToDate(Int64 cachedHash) +51
System.Web.Compilation.BuildManager.ExecutePreAppStart() +132
System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters, PolicyLevel policyLevel, Exception appDomainCreationException) +521
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It is happning even you are providing the trust level as full like below.
<system.Web>
...
<trust level="Full"/>
...
</system.Web>
-----------------------------------------------
And fix for that is
You need to contact the big rocks supporting team as your site need the configuration of 4.7 , as it is build in MVC 5.0 + version so just check with them and they will give CAS access to full. Even if you do setting in PLSK it wont work they will provide it to you.