An issue was discovered in Joomla! before 3.8.13. com_joomlaupdate allows the execution of arbitrary code. The default ACL config enabled the ability of Administrator-level users to access com_joomlaupdate and trigger code execution.
An issue was discovered in Joomla! before 3.8.12. Inadequate checks in the InputFilter class could allow specifically prepared phar files to pass the upload filter.
An XSS issue was discovered in the language switcher module in Joomla! 1.6.0 through 3.8.8 before 3.8.9. In some cases, the link of the current language might contain unescaped HTML special characters. This may lead to reflective XSS via injection of arbitrary parameters and/or values on the current page URL.
An issue was discovered in Joomla! 2.5.0 through 3.8.8 before 3.8.9. The autoload code checks classnames to be valid, using the "class_exists" function in PHP. In PHP 5.3, this function validates invalid names as valid, which can result in a Local File Inclusion.
An issue was discovered in com_fields in Joomla! Core before 3.8.8. Inadequate filtering allows users authorised to create custom fields to manipulate the filtering options and inject an unvalidated option.
An issue was discovered in Joomla! Core before 3.8.8. Depending on the server configuration, PHAR files might be handled as executable PHP scripts by the webserver.