Services/Form/classes/class.ilDateDurationInputGUI.php and Services/Form/classes/class.ilDateTimeInputGUI.php in ILIAS 5.1.x through 5.3.x before 5.3.4 allow XSS via an invalid date.
The RSS subsystem in ILIAS 5.1.x, 5.2.x, and 5.3.x before 5.3.5 has XSS via a URI to Services/Feeds/classes/class.ilExternalFeedItem.php.
Services/Feeds/classes/class.ilExternalFeedItem.php in ILIAS 5.1.x, 5.2.x, and 5.3.x before 5.3.5 has XSS via a link attribute.
ILIAS 5.1.x, 5.2.x, and 5.3.x before 5.3.5 redirects a logged-in user to a third-party site via the returntourl parameter.
Services/COPage/classes/class.ilPCSourceCode.php in ILIAS 5.1.x, 5.2.x, and 5.3.x before 5.3.5 has XSS.