Merge branch 'MAGETWO-88659' into 2.1.15-bugfixes-010818

Author: Dmytro Voskoboinikov

app/code/Magento/Widget/Block/Adminhtml/Widget/Chooser.php

@@ -180,7 +180,7 @@ protected function _toHtml()
             <label class="widget-option-label" id="' .
             $chooserId .
             'label">' .
-            ($this->getLabel() ? $this->getLabel() : __(
+            ($this->getLabel() ? $this->escapeHtml($this->getLabel()) : __(
                 'Not Selected'
             )) .
             '</label>