Fix security vulnerability in account management API

src/main/java/de/thm/arsnova/controller/UserController.java

@@ -95,7 +95,7 @@ public class UserController extends AbstractController {
 		response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
 	}
 
-	@RequestMapping(value = { "/{username}" }, method = RequestMethod.DELETE)
+	@RequestMapping(value = { "/{username}/" }, method = RequestMethod.DELETE)
 	public final void activate(
 			@PathVariable final String username,
 			final HttpServletRequest request,

src/main/java/de/thm/arsnova/services/UserService.java

@@ -408,7 +408,7 @@ public class UserService implements IUserService {
 	public DbUser deleteDbUser(String username) {
 		User user = getCurrentUser();
 		if (!user.getUsername().equals(username)
-				&& SecurityContextHolder.getContext().getAuthentication().getAuthorities()
+				&& !SecurityContextHolder.getContext().getAuthentication().getAuthorities()
 						.contains(new SimpleGrantedAuthority("ROLE_ADMIN"))) {
 			throw new UnauthorizedException();
 		}