diff --git a/dom/base/Document.cpp b/dom/base/Document.cpp
index 212179e8b098..306bd0eaa357 100644
--- a/dom/base/Document.cpp
+++ b/dom/base/Document.cpp
@@ -14397,26 +14397,6 @@ bool Document::HasScriptsBlockedBySandbox() {
   return mSandboxFlags & SANDBOXED_SCRIPTS;
 }
 
-bool Document::InlineScriptAllowedByCSP() {
-  // this function assumes the inline script is parser created
-  //  (e.g., before setting attribute(!) event handlers)
-  bool allowsInlineScript = true;
-  if (mCSP) {
-    nsresult rv = mCSP->GetAllowsInline(
-        nsIContentPolicy::TYPE_SCRIPT,
-        EmptyString(),  // aNonce
-        true,           // aParserCreated
-        nullptr,        // aTriggeringElement
-        nullptr,        // aCSPEventListener
-        EmptyString(),  // FIXME get script sample (bug 1314567)
-        0,              // aLineNumber
-        0,              // aColumnNumber
-        &allowsInlineScript);
-    NS_ENSURE_SUCCESS(rv, true);
-  }
-  return allowsInlineScript;
-}
-
 // Some use-counter sanity-checking.
 static_assert(size_t(eUseCounter_EndCSSProperties) -
                       size_t(eUseCounter_FirstCSSProperty) ==
diff --git a/dom/base/Document.h b/dom/base/Document.h
index 710f4c53567f..66f9e2785c32 100644
--- a/dom/base/Document.h
+++ b/dom/base/Document.h
@@ -3566,8 +3566,6 @@ class Document : public nsINode,
 
   bool HasScriptsBlockedBySandbox();
 
-  bool InlineScriptAllowedByCSP();
-
   void ReportHasScrollLinkedEffect();
   bool HasScrollLinkedEffect() const { return mHasScrollLinkedEffect; }
 
diff --git a/dom/webidl/Document.webidl b/dom/webidl/Document.webidl
index 2dbc16208a1d..9035b2aa6c29 100644
--- a/dom/webidl/Document.webidl
+++ b/dom/webidl/Document.webidl
@@ -575,14 +575,6 @@ partial interface Document {
   void setSuppressedEventListener(EventListener? aListener);
 };
 
-// Extension to give chrome and XBL JS the ability to determine whether
-// the document is sandboxed without permission to run scripts
-// and whether inline scripts are blocked by the document's CSP.
-partial interface Document {
-  [Func="IsChromeOrXBL"] readonly attribute boolean hasScriptsBlockedBySandbox;
-  [Func="IsChromeOrXBL"] readonly attribute boolean inlineScriptAllowedByCSP;
-};
-
 // Allows frontend code to query a CSP which needs to be passed for a
 // new load into docshell. Further, allows to query the CSP in JSON
 // format for testing purposes.