--- a/dom/base/nsDocument.cpp
+++ b/dom/base/nsDocument.cpp
@@ -1569,16 +1569,25 @@ nsDocument::~nsDocument()
       } else if (hasMixedActive){
         mixedContentLevel = MIXED_ACTIVE_CONTENT;
       } else if (hasMixedDisplay) {
         mixedContentLevel = MIXED_DISPLAY_CONTENT;
       }
       Accumulate(Telemetry::MIXED_CONTENT_PAGE_LOAD, mixedContentLevel);
 
       Accumulate(Telemetry::SCROLL_LINKED_EFFECT_FOUND, mHasScrollLinkedEffect);
+
+      // record mixed object subrequest telemetry
+      if (mHasMixedContentObjectSubrequest) {
+        /* mixed object subrequest loaded on page*/
+        Accumulate(Telemetry::MIXED_CONTENT_OBJECT_SUBREQUEST, 1);
+      } else {
+        /* no mixed object subrequests loaded on page*/
+        Accumulate(Telemetry::MIXED_CONTENT_OBJECT_SUBREQUEST, 0);
+      }
     }
   }
 
   ReportUseCounters();
 
   mInDestructor = true;
   mInUnlinkOrDeletion = true;
 

--- a/dom/base/nsIDocument.h
+++ b/dom/base/nsIDocument.h
@@ -606,16 +606,24 @@ public:
    * Set the mixed display content blocked flag for this document.
    */
   void SetHasMixedDisplayContentBlocked(bool aHasMixedDisplayContentBlocked)
   {
     mHasMixedDisplayContentBlocked = aHasMixedDisplayContentBlocked;
   }
 
   /**
+   * Set the mixed content object subrequest flag for this document.
+   */
+  void SetHasMixedContentObjectSubrequest(bool aHasMixedContentObjectSubrequest)
+  {
+    mHasMixedContentObjectSubrequest = aHasMixedContentObjectSubrequest;
+  }
+
+  /**
    * Get tracking content blocked flag for this document.
    */
   bool GetHasTrackingContentBlocked()
   {
     return mHasTrackingContentBlocked;
   }
 
   /**
@@ -2902,16 +2910,19 @@ protected:
   bool mHasMixedActiveContentBlocked : 1;
 
   // True if a document has loaded Mixed Display/Passive Content (see nsMixedContentBlocker.cpp)
   bool mHasMixedDisplayContentLoaded : 1;
 
   // True if a document has blocked Mixed Display/Passive Content (see nsMixedContentBlocker.cpp)
   bool mHasMixedDisplayContentBlocked : 1;
 
+  // True if a document loads a plugin object that attempts to load mixed content subresources through necko(see nsMixedContentBlocker.cpp)
+  bool mHasMixedContentObjectSubrequest : 1;
+
   // True if a document has blocked Tracking Content
   bool mHasTrackingContentBlocked : 1;
 
   // True if a document has loaded Tracking Content
   bool mHasTrackingContentLoaded : 1;
 
   // True if DisallowBFCaching has been called on this document.
   bool mBFCacheDisallowed : 1;

--- a/dom/security/nsMixedContentBlocker.cpp
+++ b/dom/security/nsMixedContentBlocker.cpp
@@ -768,16 +768,21 @@ nsMixedContentBlocker::ShouldLoad(bool a
       if (cc) {
         mozilla::ipc::URIParams uri;
         SerializeURI(aContentLocation, uri);
         cc->SendAccumulateMixedContentHSTS(uri, active);
       }
     }
   }
 
+  // set hasMixedContentObjectSubrequest on this object if necessary
+  if (aContentType == TYPE_OBJECT_SUBREQUEST) {
+    rootDoc->SetHasMixedContentObjectSubrequest(true);
+  }
+
   // If the content is display content, and the pref says display content should be blocked, block it.
   if (sBlockMixedDisplay && classification == eMixedDisplay) {
     if (allowMixedContent) {
       LogMixedContentMessage(classification, aContentLocation, rootDoc, eUserOverride);
       *aDecision = nsIContentPolicy::ACCEPT;
       // See if mixed display content has already loaded on the page or if the state needs to be updated here.
       // If mixed display hasn't loaded previously, then we need to call OnSecurityChange() to update the UI.
       if (rootDoc->GetHasMixedDisplayContentLoaded()) {

--- a/toolkit/components/telemetry/Histograms.json
+++ b/toolkit/components/telemetry/Histograms.json
@@ -7785,16 +7785,24 @@
   },
   "MIXED_CONTENT_HSTS": {
     "alert_emails": ["seceng@mozilla.org"],
     "expires_in_version": "never",
     "kind": "enumerated",
     "n_values": 10,
     "description": "How often would blocked mixed content be allowed if HSTS upgrades were allowed? 0=display/no-HSTS, 1=display/HSTS, 2=active/no-HSTS, 3=active/HSTS"
   },
+  "MIXED_CONTENT_OBJECT_SUBREQUEST": {
+    "alert_emails": ["seceng@mozilla.org"],
+    "bug_numbers": [1244116],
+    "expires_in_version": "55",
+    "kind": "enumerated",
+    "n_values": 10,
+    "description": "How often objects load insecure content on secure pages (counting pages, not objects). 0=pages with no mixed object subrequests, 1=pages with mixed object subrequests"
+  },
   "COOKIE_SCHEME_SECURITY": {
     "alert_emails": ["seceng@mozilla.org"],
     "expires_in_version": "50",
     "kind": "enumerated",
     "n_values": 10,
     "releaseChannelCollection": "opt-out",
     "description": "How often are secure cookies set from non-secure origins, and vice-versa? 0=nonsecure/http, 1=nonsecure/https, 2=secure/http, 3=secure/https"
   },