diff --git a/widget/ContentCache.cpp b/widget/ContentCache.cpp
index ece057c42594..df5748cb8a04 100644
--- a/widget/ContentCache.cpp
+++ b/widget/ContentCache.cpp
@@ -76,6 +76,41 @@ bool ContentCache::IsValid() const {
   return true;
 }
 
+void ContentCache::AssertIfInvalid() const {
+#if MOZ_DIAGNOSTIC_ASSERT_ENABLED
+  if (IsValid()) {
+    return;
+  }
+
+  // This text will appear in the crash reports without any permissions.
+  // Do not use `ToString` here to avoid to expose unexpected data with
+  // changing the type or `operator<<()`.
+  nsPrintfCString info(
+      "ContentCache={ mText=%s, mSelection=%s, mCaret=%s, mTextRectArray=%s, "
+      "mCompositionStart=%s }\n",
+      // Don't expose mText.ref() value for protecting the user's privacy.
+      mText.isNothing()
+          ? "Nothing"
+          : nsPrintfCString("{ Length()=%zu }", mText->Length()).get(),
+      mSelection.isNothing()
+          ? "Nothing"
+          : nsPrintfCString("{ mAnchor=%u, mFocus=%u }", mSelection->mAnchor,
+                            mSelection->mFocus)
+                .get(),
+      mCaret.isNothing()
+          ? "Nothing"
+          : nsPrintfCString("{ mOffset=%u }", mCaret->mOffset).get(),
+      mTextRectArray.isNothing()
+          ? "Nothing"
+          : nsPrintfCString("{ Length()=%u }", mTextRectArray->Length()).get(),
+      mCompositionStart.isNothing()
+          ? "Nothing"
+          : nsPrintfCString("%u", mCompositionStart.value()).get());
+  CrashReporter::AppendAppNotesToCrashReport(info);
+  MOZ_DIAGNOSTIC_ASSERT(false, "Invalid ContentCache data");
+#endif  // #if MOZ_DIAGNOSTIC_ASSERT_ENABLED
+}
+
 /*****************************************************************************
  * mozilla::ContentCacheInChild
  *****************************************************************************/
@@ -148,7 +183,7 @@ bool ContentCacheInChild::CacheAll(nsIWidget* aWidget,
 
   const bool textCached = CacheText(aWidget, aNotification);
   const bool editorRectCached = CacheEditorRect(aWidget, aNotification);
-  MOZ_DIAGNOSTIC_ASSERT(IsValid());
+  AssertIfInvalid();
   return (textCached || editorRectCached) && IsValid();
 }
 
@@ -190,7 +225,7 @@ bool ContentCacheInChild::CacheSelection(nsIWidget* aWidget,
             ("0x%p CacheSelection(), FAILED, editable content had already been "
              "blurred",
              this));
-    MOZ_DIAGNOSTIC_ASSERT(IsValid());
+    AssertIfInvalid();
     return false;
   } else {
     mSelection.emplace(querySelectedTextEvent);
@@ -233,7 +268,7 @@ bool ContentCacheInChild::CacheCaret(nsIWidget* aWidget,
   MOZ_LOG(sContentCacheLog, LogLevel::Info,
           ("0x%p   CacheCaret(), Succeeded, mSelection=%s, mCaret=%s", this,
            ToString(mSelection).c_str(), ToString(mCaret).c_str()));
-  MOZ_DIAGNOSTIC_ASSERT(IsValid());
+  AssertIfInvalid();
   return IsValid();
 }
 
@@ -278,7 +313,7 @@ bool ContentCacheInChild::CacheCaretAndTextRects(
 
   const bool caretCached = CacheCaret(aWidget, aNotification);
   const bool textRectsCached = CacheTextRects(aWidget, aNotification);
-  MOZ_DIAGNOSTIC_ASSERT(IsValid());
+  AssertIfInvalid();
   return (caretCached || textRectsCached) && IsValid();
 }
 
@@ -340,7 +375,7 @@ bool ContentCacheInChild::CacheText(nsIWidget* aWidget,
     mSelection.reset();
     mCaret.reset();
     mTextRectArray.reset();
-    MOZ_DIAGNOSTIC_ASSERT(IsValid());
+    AssertIfInvalid();
     return false;
   }
 
@@ -615,7 +650,7 @@ bool ContentCacheInChild::CacheTextRects(nsIWidget* aWidget,
        ToString(mTextRectArray).c_str(), ToString(mSelection).c_str(),
        ToString(mFirstCharRect).c_str(),
        ToString(mLastCommitStringTextRectArray).c_str()));
-  MOZ_DIAGNOSTIC_ASSERT(IsValid());
+  AssertIfInvalid();
   return IsValid();
 }
 
diff --git a/widget/ContentCache.h b/widget/ContentCache.h
index 332ff9ff4312..3f8b48425ede 100644
--- a/widget/ContentCache.h
+++ b/widget/ContentCache.h
@@ -48,6 +48,8 @@ class ContentCache {
   [[nodiscard]] bool IsValid() const;
 
  protected:
+  void AssertIfInvalid() const;
+
   // Whole text in the target
   Maybe<nsString> mText;