OMERO.web provides a web based client and plugin infrastructure. In versions prior to 5.11.0, a variety of templates do not perform proper sanitization through HTML escaping. Due to the lack of sanitization and use of ``jQuery.html()``, there are a whole host of cross-site scripting possibilities with specially crafted input to a variety of fields. This issue is patched in version 5.11.0. There are no known workarounds aside from upgrading.