diff --git a/libraries/plugins/transformations/abs/RegexValidationTransformationsPlugin.php b/libraries/plugins/transformations/abs/RegexValidationTransformationsPlugin.php
index 63995e4a9f..caf540395c 100644
--- a/libraries/plugins/transformations/abs/RegexValidationTransformationsPlugin.php
+++ b/libraries/plugins/transformations/abs/RegexValidationTransformationsPlugin.php
@@ -50,7 +50,7 @@ abstract class RegexValidationTransformationsPlugin extends IOTransformationsPlu
             $this->success = false;
             $this->error = sprintf(
                 __('Validation failed for the input string %s.'),
-                $buffer
+                htmlspecialchars($buffer)
             );
         }