In Joomla! before 3.9.19, lack of input validation in the heading tag option of the "Articles - Newsflash" and "Articles - Categories" modules allows XSS.
An issue was discovered in Joomla! before 3.9.17. Incorrect ACL checks in the access level section of com_users allow the unauthorized deletion of usergroups.
An issue was discovered in Joomla! before 3.9.16. Various actions in com_templates lack the required ACL checks, leading to various potential attack vectors.
An issue was discovered in Joomla! before 3.9.16. Missing length checks in the user table can lead to the creation of users with duplicate usernames and/or email addresses.