--- a/ipc/glue/GeckoChildProcessHost.cpp
+++ b/ipc/glue/GeckoChildProcessHost.cpp
@@ -1112,19 +1112,20 @@ GeckoChildProcessHost::PerformAsyncLaunc
         cmdLine.command_line_string().c_str());
     }
   } else
 #endif
   {
     base::LaunchApp(cmdLine, false, false, &process);
 
 #ifdef MOZ_SANDBOX
-    // We need to be able to duplicate handles to non-sandboxed content
+    // We need to be able to duplicate handles to non-sandboxed content and GMP
     // processes, so add it as a target peer.
-    if (mProcessType == GeckoProcessType_Content) {
+    if (mProcessType == GeckoProcessType_Content ||
+        mProcessType == GeckoProcessType_GMPlugin) {
       if (!mSandboxBroker.AddTargetPeer(process)) {
         NS_WARNING("Failed to add content process as target peer.");
       }
     }
 #endif
   }
 
 #else

--- a/security/sandbox/win/src/sandboxbroker/sandboxBroker.cpp
+++ b/security/sandbox/win/src/sandboxbroker/sandboxBroker.cpp
@@ -183,23 +183,28 @@ SandboxBroker::SetSecurityLevelForConten
   // The content process needs to be able to duplicate named pipes back to the
   // broker process, which are File type handles.
   result = mPolicy->AddRule(sandbox::TargetPolicy::SUBSYS_HANDLES,
                             sandbox::TargetPolicy::HANDLES_DUP_BROKER,
                             L"File");
   MOZ_RELEASE_ASSERT(sandbox::SBOX_ALL_OK == result,
                      "With these static arguments AddRule should never fail, what happened?");
 
-  // The content process needs to be able to duplicate shared memory to the
-  // broker process, which are Section type handles.
+  // The content process needs to be able to duplicate shared memory handles,
+  // which are Section handles, to the broker process and other child processes.
   result = mPolicy->AddRule(sandbox::TargetPolicy::SUBSYS_HANDLES,
                             sandbox::TargetPolicy::HANDLES_DUP_BROKER,
                             L"Section");
   MOZ_RELEASE_ASSERT(sandbox::SBOX_ALL_OK == result,
                      "With these static arguments AddRule should never fail, what happened?");
+  result = mPolicy->AddRule(sandbox::TargetPolicy::SUBSYS_HANDLES,
+                            sandbox::TargetPolicy::HANDLES_DUP_ANY,
+                            L"Section");
+  MOZ_RELEASE_ASSERT(sandbox::SBOX_ALL_OK == result,
+                     "With these static arguments AddRule should never fail, what happened?");
 }
 #endif
 
 #define SANDBOX_ENSURE_SUCCESS(result, message) \
   do { \
     MOZ_ASSERT(sandbox::SBOX_ALL_OK == result, message); \
     if (sandbox::SBOX_ALL_OK != result) \
       return false; \