diff --git a/editor/libeditor/HTMLAbsPositionEditor.cpp b/editor/libeditor/HTMLAbsPositionEditor.cpp
index 2378d243dd1e..52cf72af5e42 100644
--- a/editor/libeditor/HTMLAbsPositionEditor.cpp
+++ b/editor/libeditor/HTMLAbsPositionEditor.cpp
@@ -135,6 +135,12 @@ NS_IMETHODIMP HTMLEditor::SetAbsolutePositioningEnabled(bool aIsEnabled) {
   return NS_OK;
 }
 
+NS_IMETHODIMP HTMLEditor::GetIsAbsolutePositioningActive(bool* aIsActive) {
+  MOZ_ASSERT(aIsActive);
+  *aIsActive = !!mAbsolutelyPositionedObject;
+  return NS_OK;
+}
+
 Result<int32_t, nsresult> HTMLEditor::AddZIndexWithTransaction(
     nsStyledElement& aStyledElement, int32_t aChange) {
   if (!aChange) {
diff --git a/editor/libeditor/HTMLAnonymousNodeEditor.cpp b/editor/libeditor/HTMLAnonymousNodeEditor.cpp
index f89b4e334ab7..f2e6dca7ca64 100644
--- a/editor/libeditor/HTMLAnonymousNodeEditor.cpp
+++ b/editor/libeditor/HTMLAnonymousNodeEditor.cpp
@@ -12,6 +12,7 @@
 #include "mozilla/PresShellInlines.h"
 #include "mozilla/dom/BindContext.h"
 #include "mozilla/dom/Element.h"
+#include "mozilla/dom/ElementInlines.h"
 #include "mozilla/dom/EventTarget.h"
 #include "mozilla/mozalloc.h"
 #include "nsAString.h"
@@ -292,31 +293,44 @@ void HTMLEditor::HideAnonymousEditingUIs() {
 void HTMLEditor::HideAnonymousEditingUIsIfUnnecessary() {
   // XXX Perhaps, this is wrong approach to hide multiple UIs because
   //     hiding one UI may causes overwriting existing UI with newly
-  //     created one.  In such case, we will leak ovewritten UI.
-  if (!IsAbsolutePositionEditorEnabled() && mAbsolutelyPositionedObject) {
-    // XXX If we're moving something, we need to cancel or commit the
-    //     operation now.
-    HideGrabberInternal();
-    NS_ASSERTION(!mAbsolutelyPositionedObject,
-                 "HTMLEditor::HideGrabberInternal() failed, but ignored");
+  //     created one.  In such case, we will leak overwritten UI.
+  if (mAbsolutelyPositionedObject) {
+    const Element* const editingHost =
+        mAbsolutelyPositionedObject->GetEditingHost();
+    if (!IsAbsolutePositionEditorEnabled() || !editingHost ||
+        editingHost->IsContentEditablePlainTextOnly()) {
+      // XXX If we're moving something, we need to cancel or commit the
+      //     operation now.
+      HideGrabberInternal();
+      NS_ASSERTION(!mAbsolutelyPositionedObject,
+                   "HTMLEditor::HideGrabberInternal() failed, but ignored");
+    }
   }
-  if (!IsInlineTableEditorEnabled() && mInlineEditedCell) {
-    // XXX If we're resizing a table element, we need to cancel or commit the
-    //     operation now.
-    HideInlineTableEditingUIInternal();
-    NS_ASSERTION(
-        !mInlineEditedCell,
-        "HTMLEditor::HideInlineTableEditingUIInternal() failed, but ignored");
+  if (mInlineEditedCell) {
+    const Element* const editingHost = mInlineEditedCell->GetEditingHost();
+    if (!IsInlineTableEditorEnabled() || !editingHost ||
+        editingHost->IsContentEditablePlainTextOnly()) {
+      // XXX If we're resizing a table element, we need to cancel or commit the
+      //     operation now.
+      HideInlineTableEditingUIInternal();
+      NS_ASSERTION(
+          !mInlineEditedCell,
+          "HTMLEditor::HideInlineTableEditingUIInternal() failed, but ignored");
+    }
   }
-  if (!IsObjectResizerEnabled() && mResizedObject) {
-    // XXX If we're resizing something, we need to cancel or commit the
-    //     operation now.
-    DebugOnly<nsresult> rvIgnored = HideResizersInternal();
-    NS_WARNING_ASSERTION(
-        NS_SUCCEEDED(rvIgnored),
-        "HTMLEditor::HideResizersInternal() failed, but ignored");
-    NS_ASSERTION(!mResizedObject,
-                 "HTMLEditor::HideResizersInternal() failed, but ignored");
+  if (mResizedObject) {
+    const Element* const editingHost = mResizedObject->GetEditingHost();
+    if (!IsObjectResizerEnabled() || !editingHost ||
+        editingHost->IsContentEditablePlainTextOnly()) {
+      // XXX If we're resizing something, we need to cancel or commit the
+      //     operation now.
+      DebugOnly<nsresult> rvIgnored = HideResizersInternal();
+      NS_WARNING_ASSERTION(
+          NS_SUCCEEDED(rvIgnored),
+          "HTMLEditor::HideResizersInternal() failed, but ignored");
+      NS_ASSERTION(!mResizedObject,
+                   "HTMLEditor::HideResizersInternal() failed, but ignored");
+    }
   }
 }
 
@@ -361,6 +375,13 @@ nsresult HTMLEditor::RefreshEditingUI() {
     return NS_OK;
   }
 
+  const RefPtr<Element> editingHost =
+      ComputeEditingHost(LimitInBodyElement::No);
+  if (editingHost && editingHost->IsContentEditablePlainTextOnly()) {
+    return NS_OK;
+  }
+  MOZ_ASSERT(editingHost == selectionContainerElement->GetEditingHost());
+
   // what's its tag?
   RefPtr<Element> focusElement = std::move(selectionContainerElement);
   nsAtom* focusTagAtom = focusElement->NodeInfo()->NameAtom();
@@ -443,11 +464,9 @@ nsresult HTMLEditor::RefreshEditingUI() {
   }
 
   // now, let's display all contextual UI for good
-  nsIContent* hostContent = ComputeEditingHost();
-
   if (IsObjectResizerEnabled() && focusElement &&
       HTMLEditUtils::IsSimplyEditableNode(*focusElement) &&
-      focusElement != hostContent) {
+      focusElement != editingHost) {
     if (nsGkAtoms::img == focusTagAtom) {
       mResizedObjectIsAnImage = true;
     }
@@ -468,7 +487,7 @@ nsresult HTMLEditor::RefreshEditingUI() {
 
   if (IsAbsolutePositionEditorEnabled() && absPosElement &&
       HTMLEditUtils::IsSimplyEditableNode(*absPosElement) &&
-      absPosElement != hostContent) {
+      absPosElement != editingHost) {
     if (mAbsolutelyPositionedObject) {
       nsresult rv = RefreshGrabberInternal();
       if (NS_FAILED(rv)) {
@@ -487,7 +506,7 @@ nsresult HTMLEditor::RefreshEditingUI() {
   // XXX Shouldn't we check whether the `<table>` element is editable or not?
   if (IsInlineTableEditorEnabled() && cellElement &&
       HTMLEditUtils::IsSimplyEditableNode(*cellElement) &&
-      cellElement != hostContent) {
+      cellElement != editingHost) {
     if (mInlineEditedCell) {
       nsresult rv = RefreshInlineTableEditingUIInternal();
       if (NS_FAILED(rv)) {
diff --git a/editor/libeditor/HTMLEditorObjectResizer.cpp b/editor/libeditor/HTMLEditorObjectResizer.cpp
index 8a11c8487c1c..a9b9cc3c828f 100644
--- a/editor/libeditor/HTMLEditorObjectResizer.cpp
+++ b/editor/libeditor/HTMLEditorObjectResizer.cpp
@@ -1481,6 +1481,12 @@ NS_IMETHODIMP HTMLEditor::SetObjectResizingEnabled(
   return NS_OK;
 }
 
+NS_IMETHODIMP HTMLEditor::GetIsObjectResizingActive(bool* aIsActive) {
+  MOZ_ASSERT(aIsActive);
+  *aIsActive = !!mResizedObject;
+  return NS_OK;
+}
+
 #undef kTopLeft
 #undef kTop
 #undef kTopRight
diff --git a/editor/libeditor/HTMLInlineTableEditor.cpp b/editor/libeditor/HTMLInlineTableEditor.cpp
index 434854e10be3..16d5b2cc91f3 100644
--- a/editor/libeditor/HTMLInlineTableEditor.cpp
+++ b/editor/libeditor/HTMLInlineTableEditor.cpp
@@ -31,6 +31,12 @@ NS_IMETHODIMP HTMLEditor::GetInlineTableEditingEnabled(bool* aIsEnabled) {
   return NS_OK;
 }
 
+NS_IMETHODIMP HTMLEditor::GetIsInlineTableEditingActive(bool* aIsActive) {
+  MOZ_ASSERT(aIsActive);
+  *aIsActive = !!mInlineEditedCell;
+  return NS_OK;
+}
+
 nsresult HTMLEditor::ShowInlineTableEditingUIInternal(Element& aCellElement) {
   if (NS_WARN_IF(!HTMLEditUtils::IsTableCell(&aCellElement))) {
     return NS_OK;
diff --git a/editor/libeditor/tests/mochitest.toml b/editor/libeditor/tests/mochitest.toml
index 8d82343f7acb..a0b1a781c250 100644
--- a/editor/libeditor/tests/mochitest.toml
+++ b/editor/libeditor/tests/mochitest.toml
@@ -444,6 +444,8 @@ skip-if = ["os == 'android'"] # Needs interaction with the scrollbar
 
 ["test_dragend_target.html"]
 
+["test_editing_UI_in_plaintext-only.html"]
+
 ["test_execCommandPaste_noTarget.html"]
 
 ["test_focus_caret_navigation_between_nested_editors.html"]
diff --git a/editor/libeditor/tests/test_editing_UI_in_plaintext-only.html b/editor/libeditor/tests/test_editing_UI_in_plaintext-only.html
new file mode 100644
index 000000000000..63ef371a193b
--- /dev/null
+++ b/editor/libeditor/tests/test_editing_UI_in_plaintext-only.html
@@ -0,0 +1,95 @@
+<!doctype html>
+<html>
+<head>
+<meta charset="utf-8">
+<title></title>
+<script src="/tests/SimpleTest/SimpleTest.js"></script>
+<script src="/tests/SimpleTest/EventUtils.js"></script>
+<link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+<script>
+"use strict";
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.waitForFocus(async () => {
+  await SpecialPowers.pushPrefEnv({
+    set: [["dom.element.contenteditable.plaintext-only.enabled", true]],
+  });
+  function waitForTick() {
+    return new Promise(resolve => requestAnimationFrame(() => requestAnimationFrame(resolve)));
+  }
+  await (async () => {
+    const editingHost = document.getElementById("testAbs");
+    editingHost.contentEditable = "plaintext-only";
+    editingHost.focus();
+    document.execCommand("enableAbsolutePositionEditing", false, "true");
+    const target = editingHost.querySelector("div[style]");
+    synthesizeMouseAtCenter(target, {});
+    await waitForTick();
+    is(
+      getHTMLEditor().isAbsolutePositioningActive,
+      false,
+      "The absolutely positioned element positioner UI should not be visible"
+    );
+    document.execCommand("enableAbsolutePositionEditing", false, "false");
+    editingHost.remove();
+    await waitForTick();
+  })();
+  await (async () => {
+    const editingHost = document.getElementById("testTable");
+    editingHost.contentEditable = "plaintext-only";
+    editingHost.focus();
+    document.execCommand("enableInlineTableEditing", false, "true");
+    const target = editingHost.querySelector("td");
+    synthesizeMouseAtCenter(target, {});
+    await waitForTick();
+    is(
+      getHTMLEditor().isInlineTableEditingActive,
+      false,
+      "The inline table editing UI should not be visible"
+    );
+    document.execCommand("enableInlineTableEditing", false, "false");
+    editingHost.remove();
+    await waitForTick();
+  })();
+  await (async () => {
+    const editingHost = document.getElementById("testResizer");
+    editingHost.contentEditable = "plaintext-only";
+    editingHost.focus();
+    document.execCommand("enableObjectResizing", false, "true");
+    const target = editingHost.querySelector("img");
+    synthesizeMouseAtCenter(target, {});
+    await waitForTick();
+    is(
+      getHTMLEditor().isObjectResizingActive,
+      false,
+      "The image resizer UI should not be visible"
+    );
+    document.execCommand("enableObjectResizing", false, "false");
+    editingHost.remove();
+    await waitForTick();
+  })();
+  SimpleTest.finish();
+});
+
+function getHTMLEditor() {
+  const Ci = SpecialPowers.Ci;
+  const editingSession = SpecialPowers.wrap(window).docShell.editingSession;
+  return editingSession.getEditorForWindow(window)
+    .QueryInterface(Ci.nsIHTMLAbsPosEditor)
+    .QueryInterface(Ci.nsIHTMLInlineTableEditor)
+    .QueryInterface(Ci.nsIHTMLObjectResizer);
+}
+</script>
+</head>
+<body>
+<div id="testAbs" style="position: absolute; width: 150px; height: 150px">
+  <div style="position: absolute; width: 100px; height: 100px"><br></div>
+</div>
+<div id="testTable">
+  <table><td><br></td></table>
+</div>
+<div id="testResizer">
+  <img src="green.png">
+</div>
+</body>
+</html>
diff --git a/editor/nsIHTMLAbsPosEditor.idl b/editor/nsIHTMLAbsPosEditor.idl
index e04c13a3b575..3106b6ce0916 100644
--- a/editor/nsIHTMLAbsPosEditor.idl
+++ b/editor/nsIHTMLAbsPosEditor.idl
@@ -15,6 +15,11 @@ interface nsIHTMLAbsPosEditor : nsISupports
   [setter_can_run_script]
   attribute boolean absolutePositioningEnabled;
 
+  /**
+   * true if the grabber to drag the absolutly positioned element is visible.
+   */
+  [infallible] readonly attribute boolean isAbsolutePositioningActive;
+
 
   /* Utility methods */
 
diff --git a/editor/nsIHTMLInlineTableEditor.idl b/editor/nsIHTMLInlineTableEditor.idl
index 479dbb2b3010..a0f7e732c723 100644
--- a/editor/nsIHTMLInlineTableEditor.idl
+++ b/editor/nsIHTMLInlineTableEditor.idl
@@ -17,4 +17,9 @@ interface nsIHTMLInlineTableEditor : nsISupports
    */
   [setter_can_run_script]
   attribute boolean inlineTableEditingEnabled;
+
+  /**
+   * true if the inline table editing UI is visible.
+   */
+  [infallible] readonly attribute boolean isInlineTableEditingActive;
 };
diff --git a/editor/nsIHTMLObjectResizer.idl b/editor/nsIHTMLObjectResizer.idl
index 120fa06b8452..4c2185b24029 100644
--- a/editor/nsIHTMLObjectResizer.idl
+++ b/editor/nsIHTMLObjectResizer.idl
@@ -29,6 +29,11 @@ interface nsIHTMLObjectResizer : nsISupports
   [setter_can_run_script]
   attribute boolean objectResizingEnabled;
 
+  /**
+   * true if the object resizing UI is visible.
+   */
+  [infallible] readonly attribute boolean isObjectResizingActive;
+
   /**
    * Hide resizers if they are visible.  If this is called while there is no
    * visible resizers, this does not throw exception, just does nothing.