Bumped version, updated changelog

doc/changelog.rst

 Changelog
 =========
 
-next release
+1.5.3
 -----
 
+* Fixed XSS vulnerability
 * Support nested categories in the navbar menu
 * SQLAlchemy
     * sort on multiple columns with `column_default_sort`
@@ -18,6 +19,7 @@ next release
     * handle special characters in filename
     * fix a bug with listing directories on Windows
     * avoid raising an exception when unknown sort parameter is encountered
+* WTForms 3 support
 
 1.5.2
 -----

flask_admin/__init__.py

-__version__ = '1.5.2'
+__version__ = '1.5.3'
 __author__ = 'Flask-Admin team'
 __email__ = 'serge.koval+github@gmail.com'