diff --git a/dom/base/Element.cpp b/dom/base/Element.cpp
index 02488cb791d4..081fc5337cf2 100644
--- a/dom/base/Element.cpp
+++ b/dom/base/Element.cpp
@@ -3291,7 +3291,7 @@ void Element::DispatchChromeOnlyLinkClickEvent(
       /* Cancelable */ true, nsGlobalWindowInner::Cast(doc->GetInnerWindow()),
       0, mouseEvent->CtrlKey(), mouseEvent->AltKey(), mouseEvent->ShiftKey(),
       mouseEvent->MetaKey(), mouseEvent->Button(), mouseDOMEvent,
-      mouseEvent->InputSource(), IgnoreErrors());
+      mouseEvent->InputSource(CallerType::System), IgnoreErrors());
   // Note: we're always trusted, but the event we pass as the `sourceEvent`
   // might not be. Frontend code will check that event's trusted property to
   // make that determination; doing it this way means we don't also start
diff --git a/dom/events/MouseEvent.cpp b/dom/events/MouseEvent.cpp
index 0a50a5c7296b..ccd71922619f 100644
--- a/dom/events/MouseEvent.cpp
+++ b/dom/events/MouseEvent.cpp
@@ -298,11 +298,22 @@ bool MouseEvent::ShiftKey() { return mEvent->AsInputEvent()->IsShift(); }
 
 bool MouseEvent::MetaKey() { return mEvent->AsInputEvent()->IsMeta(); }
 
-float MouseEvent::MozPressure() const {
+float MouseEvent::MozPressure(CallerType aCallerType) const {
+  if (nsContentUtils::ShouldResistFingerprinting(aCallerType, GetParentObject(),
+                                                 RFPTarget::PointerEvents)) {
+    // Use the spoofed value from PointerEvent::Pressure
+    return 0.5;
+  }
+
   return mEvent->AsMouseEventBase()->mPressure;
 }
 
-uint16_t MouseEvent::InputSource() const {
+uint16_t MouseEvent::InputSource(CallerType aCallerType) const {
+  if (nsContentUtils::ShouldResistFingerprinting(aCallerType, GetParentObject(),
+                                                 RFPTarget::PointerEvents)) {
+    return MouseEvent_Binding::MOZ_SOURCE_MOUSE;
+  }
+
   return mEvent->AsMouseEventBase()->mInputSource;
 }
 
diff --git a/dom/events/MouseEvent.h b/dom/events/MouseEvent.h
index 0695c1e264b4..bb0f63bad007 100644
--- a/dom/events/MouseEvent.h
+++ b/dom/events/MouseEvent.h
@@ -82,8 +82,8 @@ class MouseEvent : public UIEvent {
                                                   const MouseEventInit& aParam);
   int32_t MovementX() { return GetMovementPoint().x; }
   int32_t MovementY() { return GetMovementPoint().y; }
-  float MozPressure() const;
-  uint16_t InputSource() const;
+  float MozPressure(CallerType) const;
+  uint16_t InputSource(CallerType) const;
   void InitNSMouseEvent(const nsAString& aType, bool aCanBubble,
                         bool aCancelable, nsGlobalWindowInner* aView,
                         int32_t aDetail, int32_t aScreenX, int32_t aScreenY,
diff --git a/dom/webidl/MouseEvent.webidl b/dom/webidl/MouseEvent.webidl
index 979c05ca4961..a5fbb8b38dc8 100644
--- a/dom/webidl/MouseEvent.webidl
+++ b/dom/webidl/MouseEvent.webidl
@@ -92,7 +92,7 @@ partial interface MouseEvent
   // Finger or touch pressure event value
   // ranges between 0.0 and 1.0
   // TODO: Remove mozPressure. (bug 1534199)
-  [Deprecated="MouseEvent_MozPressure"]
+  [NeedsCallerType, Deprecated="MouseEvent_MozPressure"]
   readonly attribute float mozPressure;
 
   const unsigned short    MOZ_SOURCE_UNKNOWN    = 0;
@@ -103,10 +103,10 @@ partial interface MouseEvent
   const unsigned short    MOZ_SOURCE_TOUCH      = 5;
   const unsigned short    MOZ_SOURCE_KEYBOARD   = 6;
 
-  [ChromeOnly]
+  [NeedsCallerType, ChromeOnly]
   readonly attribute unsigned short inputSource;
 
-  [Deprecated="MozInputSource", BinaryName="inputSource"]
+  [NeedsCallerType, Deprecated="MozInputSource", BinaryName="inputSource"]
   readonly attribute unsigned short mozInputSource;
 
   // TODO: Remove initNSMouseEvent. (bug 1165213)
diff --git a/layout/forms/HTMLSelectEventListener.cpp b/layout/forms/HTMLSelectEventListener.cpp
index 8c74c57cc009..10ed410ee0eb 100644
--- a/layout/forms/HTMLSelectEventListener.cpp
+++ b/layout/forms/HTMLSelectEventListener.cpp
@@ -412,7 +412,10 @@ nsresult HTMLSelectEventListener::MouseDown(dom::Event* aMouseEvent) {
   }
 
   if (mIsCombobox) {
-    uint16_t inputSource = mouseEvent->InputSource();
+    // inputSource is used to apply padding for touch events, but
+    // the dropdown is rendered in another process, the webpage won't
+    // have access to it. It is fine to use CallerType::System here.
+    uint16_t inputSource = mouseEvent->InputSource(CallerType::System);
     if (mElement->OpenInParentProcess()) {
       nsCOMPtr<nsIContent> target = do_QueryInterface(aMouseEvent->GetTarget());
       if (target && target->IsHTMLElement(nsGkAtoms::option)) {
diff --git a/widget/nsBaseDragService.cpp b/widget/nsBaseDragService.cpp
index 98c77b4bbe3d..26d23f2f56dc 100644
--- a/widget/nsBaseDragService.cpp
+++ b/widget/nsBaseDragService.cpp
@@ -423,7 +423,7 @@ nsBaseDragService::InvokeDragSessionWithImage(
       mSourceWindowContext ? mSourceWindowContext->TopWindowContext() : nullptr;
 
   mScreenPosition = aDragEvent->ScreenPoint(CallerType::System);
-  mInputSource = aDragEvent->InputSource();
+  mInputSource = aDragEvent->InputSource(CallerType::System);
 
   // If dragging within a XUL tree and no custom drag image was
   // set, the region argument to InvokeDragSessionWithImage needs
@@ -472,7 +472,7 @@ nsBaseDragService::InvokeDragSessionWithRemoteImage(
   mSourceTopWindowContext = mDragStartData->GetSourceTopWindowContext();
 
   mScreenPosition = aDragEvent->ScreenPoint(CallerType::System);
-  mInputSource = aDragEvent->InputSource();
+  mInputSource = aDragEvent->InputSource(CallerType::System);
 
   nsresult rv = InvokeDragSession(
       aDOMNode, aPrincipal, aCsp, aCookieJarSettings, aTransferableArray,
@@ -504,7 +504,7 @@ nsBaseDragService::InvokeDragSessionWithSelection(
 
   mScreenPosition.x = aDragEvent->ScreenX(CallerType::System);
   mScreenPosition.y = aDragEvent->ScreenY(CallerType::System);
-  mInputSource = aDragEvent->InputSource();
+  mInputSource = aDragEvent->InputSource(CallerType::System);
 
   // just get the focused node from the selection
   // XXXndeakin this should actually be the deepest node that contains both