Doc: AssemblyBuilder require fully trusted environment with trusted input (#10541)

Author: buyaa-n

xml/System.Reflection.Emit/AssemblyBuilder.xml

@@ -76,7 +76,18 @@
   </Attributes>
   <Docs>
     <summary>Defines and represents a dynamic assembly.</summary>
-    <remarks>For more information about this API, see <see href="/dotnet/fundamentals/runtime-libraries/system-reflection-emit-assemblybuilder">Supplemental API remarks for AssemblyBuilder</see>.</remarks>
+    <remarks>
+      <format type="text/markdown"><![CDATA[
+
+## Remarks
+
+For more information about this API, see [Supplemental API remarks for AssemblyBuilder](/dotnet/fundamentals/runtime-libraries/system-reflection-emit-assemblybuilder).
+
+> [!WARNING]
+> `AssemblyBuilder` APIs require a fully trusted environment with trusted input, similar to other technologies such as compilers. There are no restrictions other than basic validation for generated IL that the `AssemblyBuilder` can contain. That includes validation for member name, count, and associated metadata, such as custom attributes.
+]]>
+      </format>
+    </remarks>
     <example>
       <format type="text/markdown"><![CDATA[
 The following code example shows how to define and use a dynamic assembly. The example assembly contains one type, `MyDynamicType`, that has a private field, a property that gets and sets the private field, constructors that initialize the private field, and a method that multiplies a user-supplied number by the private field value and returns the result.

xml/System.Reflection.Emit/ILGenerator.xml

@@ -84,6 +84,15 @@
 
  MSIL is used as input to a just-in-time (JIT) compiler.
 
+> [!WARNING]
+> There are no restrictions, other than basic validation, for ILGenerator APIs that produce method IL. If untrusted input is used for producing IL:
+>
+> - IL and metadata can contain secrets provided by the consumer.
+> - IL can be invalid, such as not having balanced push versus pop opcodes, or invalid operands for a given opcode.
+> - IL can contain any code that might, for example, deadlock, have infinite stack recursion, or have an infinite loop.
+> - IL can load and execute code on any other reachable assembly.
+>
+> Such code can do whatever it wishes when the method is loaded and executed. To protect against such vulnerabilities, `ILGenerator` requires a fully trusted environment with trusted input.
  ]]></format>
     </remarks>
   </Docs>

xml/System.Reflection.Emit/PersistedAssemblyBuilder.xml

@@ -25,7 +25,17 @@
   </Attributes>
   <Docs>
     <summary>Provides an AssemblyBuilder implementation that can persist assembly to a disk or stream.</summary>
-    <remarks>To be added.</remarks>
+    <remarks>
+      <format type="text/markdown"><![CDATA[
+
+## Remarks
+
+For more information about this API, see [Persisted dynamic assemblies in .NET](/dotnet/fundamentals/runtime-libraries/system-reflection-emit-persistedassemblybuilder).
+
+> [!WARNING]
+> `PersistedAssemblyBuilder` APIs require a fully trusted environment with trusted input, similar to other technologies such as compilers. There are no restrictions other than basic validation for generated IL that the `AssemblyBuilder` can contain. That includes validation for member name, count, and associated metadata, such as custom attributes.
+]]></format>
+    </remarks>
   </Docs>
   <Members>
     <Member MemberName=".ctor">