Small fixes june 2020 (#857)

* issue 849

* another integration test for a challenge

* fixing issue 848

* updated link for issue 833

* fix for 847

webgoat-lessons/xxe/src/main/resources/lessonPlans/en/XXE_changing_content_type_solution.adoc

@@ -35,7 +35,7 @@ JSON parse error: Unexpected character '{' (code 123) in prolog; expected
 
 This error message appears because we are still sending a json message towards the endpoint, so if we intercept and change change the json message to a xml message:
 
-[souce]
+[source]
 ----
 POST http://localhost:8080/WebGoat/xxe/content-type HTTP/1.1
 Content-Type: application/xml

webgoat-lessons/xxe/src/main/resources/lessonPlans/en/XXE_mitigation.adoc

@@ -20,6 +20,6 @@ xif.setProperty(XMLInputFactory.SUPPORT_DTD, true);
 For more information about configuration, see https://cheatsheetseries.owasp.org/cheatsheets/XML_External_Entity_Prevention_Cheat_Sheet.html[XXE prevention sheet]
 
 
-==== Validate
+=== Validate
 
 Implement proper validation for the Content-type and Accept header do not simply rely on the framework to handle the incoming request. If the client specifies a proper accept header return with a `406/Not Acceptable.