diff --git a/typo3/sysext/core/Documentation/Changelog/12.1/Deprecation-99031-DeprecatedFformathtmlInBackendContext.rst b/typo3/sysext/core/Documentation/Changelog/12.1/Deprecation-99031-DeprecatedFformathtmlInBackendContext.rst
new file mode 100644
index 0000000000000000000000000000000000000000..54ad4cc3078d254dcfbd6c460e552d547d0d54a0
--- /dev/null
+++ b/typo3/sysext/core/Documentation/Changelog/12.1/Deprecation-99031-DeprecatedFformathtmlInBackendContext.rst
@@ -0,0 +1,46 @@
+.. include:: /Includes.rst.txt
+
+.. _deprecation-99031-1667998430:
+
+=================================================================
+Deprecation: #99031 - Deprecated f:format.html in Backend context
+=================================================================
+
+See :issue:`99031`
+
+Description
+===========
+
+The :html:`<f:format.html />` ViewHelper :php:`TYPO3\CMS\Fluid\ViewHelpers\Format\HtmlViewHelper`
+should not be used in TYPO3 Backend context anymore.
+
+Using this ViewHelper in Backend context triggers Frontend :typoscript:`parseFunc` logic, which
+should be avoided in the backend.
+
+There are other ViewHelpers to output and parse HTML in Backend context. See description of
+the :ref:`f:sanitize.html <feature-94825-1667998632>` ViewHelper for more details.
+
+
+Impact
+======
+
+Using :html:`<f:format.html />` logs a deprecation level warning.
+
+
+Affected installations
+======================
+
+Instances with extensions that come with Backend modules using Fluid rendering and
+accessing :html:`<f:format.html />` are affected.
+
+
+Migration
+=========
+
+Switch to one of the other ViewHelpers instead, typically :html:`<f:sanitize.html />`
+to secure a given HTML string, :html:`<f:transform.html />` to parse links in HTML,
+or :html:`<f:format.raw />` to output the HTML as is when the input can be considered
+"secure".
+
+
+.. index:: Backend, Fluid, NotScanned, ext:fluid
diff --git a/typo3/sysext/core/Documentation/Changelog/9.5.x/Feature-94825-SanitizeHtmlFluidViewHelper.rst b/typo3/sysext/core/Documentation/Changelog/9.5.x/Feature-94825-SanitizeHtmlFluidViewHelper.rst
index 9613f185e23a09e50b1139bad289440bd5b3e34c..b7cb34e3fe03c5633c041bd854bf10423b7c26a1 100644
--- a/typo3/sysext/core/Documentation/Changelog/9.5.x/Feature-94825-SanitizeHtmlFluidViewHelper.rst
+++ b/typo3/sysext/core/Documentation/Changelog/9.5.x/Feature-94825-SanitizeHtmlFluidViewHelper.rst
@@ -1,5 +1,7 @@
 .. include:: /Includes.rst.txt
 
+.. _feature-94825-1667998632:
+
 ======================================================
 Feature: #94825 - New f:sanitize.html Fluid ViewHelper
 ======================================================
diff --git a/typo3/sysext/fluid/Classes/ViewHelpers/Format/HtmlViewHelper.php b/typo3/sysext/fluid/Classes/ViewHelpers/Format/HtmlViewHelper.php
index 12ef1d190bd65ce609d82c683b0ac31c3f2190dc..ba7f393066766b1eebdf778bc3b525882450ba02 100644
--- a/typo3/sysext/fluid/Classes/ViewHelpers/Format/HtmlViewHelper.php
+++ b/typo3/sysext/fluid/Classes/ViewHelpers/Format/HtmlViewHelper.php
@@ -151,10 +151,10 @@ final class HtmlViewHelper extends AbstractViewHelper
 
         /** @var RenderingContext $renderingContext */
         $request = $renderingContext->getRequest();
-        $isBackendRequest = $request instanceof ServerRequestInterface
-            && $request->getAttribute('applicationType')
-            && ApplicationType::fromRequest($request)->isBackend();
+        $isBackendRequest = $request instanceof ServerRequestInterface && ApplicationType::fromRequest($request)->isBackend();
         if ($isBackendRequest) {
+            // @deprecated since v12, remove in v13: Drop simulateFrontendEnvironment() and resetFrontendEnvironment() and throw a \RuntimeException here.
+            trigger_error('Using f:format.html in backend context has been deprecated in TYPO3 v12 and will be removed with v13', E_USER_DEPRECATED);
             $tsfeBackup = self::simulateFrontendEnvironment();
         }