diff --git a/plugins/xpcom/Makefile b/plugins/xpcom/Makefile
index 7a07984..4ee7372 100644
--- a/plugins/xpcom/Makefile
+++ b/plugins/xpcom/Makefile
@@ -49,7 +49,7 @@
 export FLAG32BIT
 
 ifeq ($(BROWSER),)
-$(warning Defaulting to FF3 build [set with BROWSER=ff3, ff3+, ff35, ff36, or ff40])
+$(warning Defaulting to FF3 build [set with BROWSER=ff3, ff3+, ff35, ff36, ff40, or ff50])
 BROWSER=ff3
 endif
 
@@ -97,14 +97,23 @@
 CFLAGS += -DGECKO_VERSION=2000
 MOZALLOC_DLLFLAGS = -lmozalloc
 MOZJS_DLLFLAGS = -lxul
-
 #FF4 drops PPC, adds x86_64. Use FLAG32BIT as a switch in the unified headers.
 ifeq ($(OS),mac)
 ALLARCHCFLAGS = -arch i386 -arch x86_64 -Xarch_i386 -DFLAG32BIT=32 -Xarch_x86_64 -DFLAG32BIT=64
 endif
-
 else
-$(error Unrecognized BROWSER of $(BROWSER) - options are ff3, ff3+, ff35, ff36, ff40)
+ifeq ($(BROWSER),ff50)
+GECKO_VERSION   = 5.0.0
+CFLAGS += -DGECKO_VERSION=5000
+MOZALLOC_DLLFLAGS = -lmozalloc
+MOZJS_DLLFLAGS = -lxul
+#FF4 drops PPC, adds x86_64. Use FLAG32BIT as a switch in the unified headers.
+ifeq ($(OS),mac)
+ALLARCHCFLAGS = -arch i386 -arch x86_64 -Xarch_i386 -DFLAG32BIT=32 -Xarch_x86_64 -DFLAG32BIT=64
+endif
+else
+$(error Unrecognized BROWSER of $(BROWSER) - options are ff3, ff3+, ff35, ff36, ff40, ff50)
+endif
 endif
 endif
 endif
@@ -178,11 +187,13 @@
 	$(MAKE) lib BROWSER=ff35 ARCH=x86
 	$(MAKE) lib BROWSER=ff36 ARCH=x86
 	$(MAKE) lib BROWSER=ff40 ARCH=x86
+	$(MAKE) lib BROWSER=ff50 ARCH=x86
 	$(MAKE) lib BROWSER=ff3 ARCH=x86_64
 	$(MAKE) lib BROWSER=ff3+ ARCH=x86_64
 	$(MAKE) lib BROWSER=ff35 ARCH=x86_64
 	$(MAKE) lib BROWSER=ff36 ARCH=x86_64
 	$(MAKE) lib BROWSER=ff40 ARCH=x86_64
+	$(MAKE) lib BROWSER=ff50 ARCH=x86_64
 
 macplatforms:
 	$(MAKE) lib BROWSER=ff3
@@ -246,6 +257,7 @@
 	@$(MAKE) $@ BROWSER=ff35
 	@$(MAKE) $@ BROWSER=ff36
 	@$(MAKE) $@ BROWSER=ff40
+	@$(MAKE) $@ BROWSER=ff50
 endif
 
 DEPEND = g++ -MM -MT'$$(OBJ_OUTDIR)/$(patsubst %.cpp,%.o,$(src))' \
diff --git a/plugins/xpcom/install-template.rdf b/plugins/xpcom/install-template.rdf
index 1586d96..0c6caff 100644
--- a/plugins/xpcom/install-template.rdf
+++ b/plugins/xpcom/install-template.rdf
@@ -12,7 +12,7 @@
       <Description>
         <em:id>{ec8030f7-c20a-464f-9b0e-13a3a9e97384}</em:id>
         <em:minVersion>3.0</em:minVersion>
-        <em:maxVersion>4.0.*</em:maxVersion>
+        <em:maxVersion>5.0.*</em:maxVersion>
       </Description>
     </em:targetApplication>
 
diff --git a/plugins/xpcom/prebuilt/extension/chrome.manifest b/plugins/xpcom/prebuilt/extension/chrome.manifest
index c787ad6..1f9b535 100644
--- a/plugins/xpcom/prebuilt/extension/chrome.manifest
+++ b/plugins/xpcom/prebuilt/extension/chrome.manifest
@@ -1,11 +1,14 @@
 content gwt-dev-plugin content/
 skin gwt-dev-plugin classic/1.0 skin/
 
-binary-component lib/Linux_x86_64-gcc3/ff40/libgwt_dev_ff40.so ABI=Linux_x86_64-gcc3
-binary-component lib/Linux_x86-gcc3/ff40/libgwt_dev_ff40.so ABI=Linux_x86-gcc3
-binary-component lib/Darwin-gcc3/ff40/libgwt_dev_ff40.dylib ABI=Darwin_x86_64-gcc3
-binary-component lib/Darwin-gcc3/ff40/libgwt_dev_ff40.dylib ABI=Darwin_x86-gcc3
-binary-component lib/WINNT_x86-msvc/ff40/xpGwtDevPlugin.dll ABI=WINNT_x86-msvc
+binary-component lib/Linux_x86_64-gcc3/ff50/libgwt_dev_ff50.so ABI=Linux_x86_64-gcc3 appversion<=5.0.*
+binary-component lib/Linux_x86-gcc3/ff50/libgwt_dev_ff50.so ABI=Linux_x86-gcc3 appversion<=5.0.*
+
+binary-component lib/Linux_x86_64-gcc3/ff40/libgwt_dev_ff40.so ABI=Linux_x86_64-gcc3 appversion<=4.0.*
+binary-component lib/Linux_x86-gcc3/ff40/libgwt_dev_ff40.so ABI=Linux_x86-gcc3 appversion<=4.0.*
+binary-component lib/Darwin-gcc3/ff40/libgwt_dev_ff40.dylib ABI=Darwin_x86_64-gcc3 appversion<=4.0.*
+binary-component lib/Darwin-gcc3/ff40/libgwt_dev_ff40.dylib ABI=Darwin_x86-gcc3 appversion<=4.0.*
+binary-component lib/WINNT_x86-msvc/ff40/xpGwtDevPlugin.dll ABI=WINNT_x86-msvc appversion<=4.0.*
 
 interfaces components/IOOPHM.xpt
 contract @gwt.google.com/ExternalWrapper;1 {028DD88B-6D65-401D-AAFD-17E497D15D09}
diff --git a/plugins/xpcom/prebuilt/extension/lib/Linux_x86-gcc3/ff3+/libgwt_dev_ff3+.so b/plugins/xpcom/prebuilt/extension/lib/Linux_x86-gcc3/ff3+/libgwt_dev_ff3+.so
index 793150e..4e2676a 100755
--- a/plugins/xpcom/prebuilt/extension/lib/Linux_x86-gcc3/ff3+/libgwt_dev_ff3+.so
+++ b/plugins/xpcom/prebuilt/extension/lib/Linux_x86-gcc3/ff3+/libgwt_dev_ff3+.so
Binary files differ
diff --git a/plugins/xpcom/prebuilt/extension/lib/Linux_x86-gcc3/ff3/libgwt_dev_ff3.so b/plugins/xpcom/prebuilt/extension/lib/Linux_x86-gcc3/ff3/libgwt_dev_ff3.so
index e075b19..a0124ac 100755
--- a/plugins/xpcom/prebuilt/extension/lib/Linux_x86-gcc3/ff3/libgwt_dev_ff3.so
+++ b/plugins/xpcom/prebuilt/extension/lib/Linux_x86-gcc3/ff3/libgwt_dev_ff3.so
Binary files differ
diff --git a/plugins/xpcom/prebuilt/extension/lib/Linux_x86-gcc3/ff35/libgwt_dev_ff35.so b/plugins/xpcom/prebuilt/extension/lib/Linux_x86-gcc3/ff35/libgwt_dev_ff35.so
index 1ff3f74..71dd54b 100755
--- a/plugins/xpcom/prebuilt/extension/lib/Linux_x86-gcc3/ff35/libgwt_dev_ff35.so
+++ b/plugins/xpcom/prebuilt/extension/lib/Linux_x86-gcc3/ff35/libgwt_dev_ff35.so
Binary files differ
diff --git a/plugins/xpcom/prebuilt/extension/lib/Linux_x86-gcc3/ff36/libgwt_dev_ff36.so b/plugins/xpcom/prebuilt/extension/lib/Linux_x86-gcc3/ff36/libgwt_dev_ff36.so
index 7037b37..ef43b34 100755
--- a/plugins/xpcom/prebuilt/extension/lib/Linux_x86-gcc3/ff36/libgwt_dev_ff36.so
+++ b/plugins/xpcom/prebuilt/extension/lib/Linux_x86-gcc3/ff36/libgwt_dev_ff36.so
Binary files differ
diff --git a/plugins/xpcom/prebuilt/extension/lib/Linux_x86-gcc3/ff40/libgwt_dev_ff40.so b/plugins/xpcom/prebuilt/extension/lib/Linux_x86-gcc3/ff40/libgwt_dev_ff40.so
index 962971f..95f4e90 100755
--- a/plugins/xpcom/prebuilt/extension/lib/Linux_x86-gcc3/ff40/libgwt_dev_ff40.so
+++ b/plugins/xpcom/prebuilt/extension/lib/Linux_x86-gcc3/ff40/libgwt_dev_ff40.so
Binary files differ
diff --git a/plugins/xpcom/prebuilt/extension/lib/Linux_x86-gcc3/ff50/libgwt_dev_ff50.so b/plugins/xpcom/prebuilt/extension/lib/Linux_x86-gcc3/ff50/libgwt_dev_ff50.so
new file mode 100755
index 0000000..c73512d
--- /dev/null
+++ b/plugins/xpcom/prebuilt/extension/lib/Linux_x86-gcc3/ff50/libgwt_dev_ff50.so
Binary files differ
diff --git a/plugins/xpcom/prebuilt/extension/lib/Linux_x86_64-gcc3/ff3+/libgwt_dev_ff3+.so b/plugins/xpcom/prebuilt/extension/lib/Linux_x86_64-gcc3/ff3+/libgwt_dev_ff3+.so
index 86509a6..26d4f76 100755
--- a/plugins/xpcom/prebuilt/extension/lib/Linux_x86_64-gcc3/ff3+/libgwt_dev_ff3+.so
+++ b/plugins/xpcom/prebuilt/extension/lib/Linux_x86_64-gcc3/ff3+/libgwt_dev_ff3+.so
Binary files differ
diff --git a/plugins/xpcom/prebuilt/extension/lib/Linux_x86_64-gcc3/ff3/libgwt_dev_ff3.so b/plugins/xpcom/prebuilt/extension/lib/Linux_x86_64-gcc3/ff3/libgwt_dev_ff3.so
index 6f6b11a..dc4dc44 100755
--- a/plugins/xpcom/prebuilt/extension/lib/Linux_x86_64-gcc3/ff3/libgwt_dev_ff3.so
+++ b/plugins/xpcom/prebuilt/extension/lib/Linux_x86_64-gcc3/ff3/libgwt_dev_ff3.so
Binary files differ
diff --git a/plugins/xpcom/prebuilt/extension/lib/Linux_x86_64-gcc3/ff35/libgwt_dev_ff35.so b/plugins/xpcom/prebuilt/extension/lib/Linux_x86_64-gcc3/ff35/libgwt_dev_ff35.so
index 7b5b53d..7b7c932 100755
--- a/plugins/xpcom/prebuilt/extension/lib/Linux_x86_64-gcc3/ff35/libgwt_dev_ff35.so
+++ b/plugins/xpcom/prebuilt/extension/lib/Linux_x86_64-gcc3/ff35/libgwt_dev_ff35.so
Binary files differ
diff --git a/plugins/xpcom/prebuilt/extension/lib/Linux_x86_64-gcc3/ff36/libgwt_dev_ff36.so b/plugins/xpcom/prebuilt/extension/lib/Linux_x86_64-gcc3/ff36/libgwt_dev_ff36.so
index aff7d35..f5aa273 100755
--- a/plugins/xpcom/prebuilt/extension/lib/Linux_x86_64-gcc3/ff36/libgwt_dev_ff36.so
+++ b/plugins/xpcom/prebuilt/extension/lib/Linux_x86_64-gcc3/ff36/libgwt_dev_ff36.so
Binary files differ
diff --git a/plugins/xpcom/prebuilt/extension/lib/Linux_x86_64-gcc3/ff40/libgwt_dev_ff40.so b/plugins/xpcom/prebuilt/extension/lib/Linux_x86_64-gcc3/ff40/libgwt_dev_ff40.so
index 596c360..20fc7a9 100755
--- a/plugins/xpcom/prebuilt/extension/lib/Linux_x86_64-gcc3/ff40/libgwt_dev_ff40.so
+++ b/plugins/xpcom/prebuilt/extension/lib/Linux_x86_64-gcc3/ff40/libgwt_dev_ff40.so
Binary files differ
diff --git a/plugins/xpcom/prebuilt/extension/lib/Linux_x86_64-gcc3/ff50/libgwt_dev_ff50.so b/plugins/xpcom/prebuilt/extension/lib/Linux_x86_64-gcc3/ff50/libgwt_dev_ff50.so
new file mode 100755
index 0000000..dd87d5e
--- /dev/null
+++ b/plugins/xpcom/prebuilt/extension/lib/Linux_x86_64-gcc3/ff50/libgwt_dev_ff50.so
Binary files differ
diff --git a/plugins/xpcom/prebuilt/ff50/include/IOOPHM.h b/plugins/xpcom/prebuilt/ff50/include/IOOPHM.h
new file mode 100644
index 0000000..0e7be5d
--- /dev/null
+++ b/plugins/xpcom/prebuilt/ff50/include/IOOPHM.h
@@ -0,0 +1,105 @@
+/*
+ * DO NOT EDIT.  THIS FILE IS GENERATED FROM IOOPHM.idl
+ */
+
+#ifndef __gen_IOOPHM_h__
+#define __gen_IOOPHM_h__
+
+
+#ifndef __gen_nsISupports_h__
+#include "nsISupports.h"
+#endif
+
+/* For IDL files that don't want to include root IDL files. */
+#ifndef NS_NO_VTABLE
+#define NS_NO_VTABLE
+#endif
+class nsIDOMWindow; /* forward declaration */
+
+
+/* starting interface:    IOOPHM */
+#define IOOPHM_IID_STR "90cef17b-c3fe-4251-af68-4381b3d938a0"
+
+#define IOOPHM_IID \
+  {0x90cef17b, 0xc3fe, 0x4251, \
+    { 0xaf, 0x68, 0x43, 0x81, 0xb3, 0xd9, 0x38, 0xa0 }}
+
+class NS_NO_VTABLE NS_SCRIPTABLE IOOPHM : public nsISupports {
+ public: 
+
+  NS_DECLARE_STATIC_IID_ACCESSOR(IOOPHM_IID)
+
+  /* boolean init (in nsIDOMWindow window); */
+  NS_SCRIPTABLE NS_IMETHOD Init(nsIDOMWindow *window, PRBool *_retval NS_OUTPARAM) = 0;
+
+  /* boolean connect (in ACString url, in ACString sessionKey, in ACString addr, in ACString moduleName, in ACString hostedHtmlVersion); */
+  NS_SCRIPTABLE NS_IMETHOD Connect(const nsACString & url, const nsACString & sessionKey, const nsACString & addr, const nsACString & moduleName, const nsACString & hostedHtmlVersion, PRBool *_retval NS_OUTPARAM) = 0;
+
+};
+
+  NS_DEFINE_STATIC_IID_ACCESSOR(IOOPHM, IOOPHM_IID)
+
+/* Use this macro when declaring classes that implement this interface. */
+#define NS_DECL_IOOPHM \
+  NS_SCRIPTABLE NS_IMETHOD Init(nsIDOMWindow *window, PRBool *_retval NS_OUTPARAM); \
+  NS_SCRIPTABLE NS_IMETHOD Connect(const nsACString & url, const nsACString & sessionKey, const nsACString & addr, const nsACString & moduleName, const nsACString & hostedHtmlVersion, PRBool *_retval NS_OUTPARAM); 
+
+/* Use this macro to declare functions that forward the behavior of this interface to another object. */
+#define NS_FORWARD_IOOPHM(_to) \
+  NS_SCRIPTABLE NS_IMETHOD Init(nsIDOMWindow *window, PRBool *_retval NS_OUTPARAM) { return _to Init(window, _retval); } \
+  NS_SCRIPTABLE NS_IMETHOD Connect(const nsACString & url, const nsACString & sessionKey, const nsACString & addr, const nsACString & moduleName, const nsACString & hostedHtmlVersion, PRBool *_retval NS_OUTPARAM) { return _to Connect(url, sessionKey, addr, moduleName, hostedHtmlVersion, _retval); } 
+
+/* Use this macro to declare functions that forward the behavior of this interface to another object in a safe way. */
+#define NS_FORWARD_SAFE_IOOPHM(_to) \
+  NS_SCRIPTABLE NS_IMETHOD Init(nsIDOMWindow *window, PRBool *_retval NS_OUTPARAM) { return !_to ? NS_ERROR_NULL_POINTER : _to->Init(window, _retval); } \
+  NS_SCRIPTABLE NS_IMETHOD Connect(const nsACString & url, const nsACString & sessionKey, const nsACString & addr, const nsACString & moduleName, const nsACString & hostedHtmlVersion, PRBool *_retval NS_OUTPARAM) { return !_to ? NS_ERROR_NULL_POINTER : _to->Connect(url, sessionKey, addr, moduleName, hostedHtmlVersion, _retval); } 
+
+#if 0
+/* Use the code below as a template for the implementation class for this interface. */
+
+/* Header file */
+class _MYCLASS_ : public IOOPHM
+{
+public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_IOOPHM
+
+  _MYCLASS_();
+
+private:
+  ~_MYCLASS_();
+
+protected:
+  /* additional members */
+};
+
+/* Implementation file */
+NS_IMPL_ISUPPORTS1(_MYCLASS_, IOOPHM)
+
+_MYCLASS_::_MYCLASS_()
+{
+  /* member initializers and constructor code */
+}
+
+_MYCLASS_::~_MYCLASS_()
+{
+  /* destructor code */
+}
+
+/* boolean init (in nsIDOMWindow window); */
+NS_IMETHODIMP _MYCLASS_::Init(nsIDOMWindow *window, PRBool *_retval NS_OUTPARAM)
+{
+    return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+/* boolean connect (in ACString url, in ACString sessionKey, in ACString addr, in ACString moduleName, in ACString hostedHtmlVersion); */
+NS_IMETHODIMP _MYCLASS_::Connect(const nsACString & url, const nsACString & sessionKey, const nsACString & addr, const nsACString & moduleName, const nsACString & hostedHtmlVersion, PRBool *_retval NS_OUTPARAM)
+{
+    return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+/* End of implementation class template. */
+#endif
+
+
+#endif /* __gen_IOOPHM_h__ */
diff --git a/plugins/xpcom/prebuilt/gwt-dev-plugin.xpi b/plugins/xpcom/prebuilt/gwt-dev-plugin.xpi
index e0f3552..9d9c522 100644
--- a/plugins/xpcom/prebuilt/gwt-dev-plugin.xpi
+++ b/plugins/xpcom/prebuilt/gwt-dev-plugin.xpi
Binary files differ
diff --git a/plugins/xpcom/prebuilt/update.rdf b/plugins/xpcom/prebuilt/update.rdf
index e8c55a4..8d90719 100644
--- a/plugins/xpcom/prebuilt/update.rdf
+++ b/plugins/xpcom/prebuilt/update.rdf
@@ -14,7 +14,7 @@
               <Description>
                 <em:id>{ec8030f7-c20a-464f-9b0e-13a3a9e97384}</em:id>
                 <em:minVersion>3.0</em:minVersion>
-                <em:maxVersion>3.5.*</em:maxVersion>
+                <em:maxVersion>5.0.*</em:maxVersion>
                 <em:updateLink>https://dl-ssl.google.com/gwt/plugins/firefox/gwt-dev-plugin.xpi</em:updateLink>
                 <em:updateInfoURL>https://dl-ssl.google.com/gwt/plugins/firefox/gwt-dev-plugin-info.xhtml?locale=%APP_LOCALE%</em:updateInfoURL>