ZF2009-02: XSS vector in Zend_Filter_StripTags
Matomo (Piwik) 0.2.33 (released Mar. 2, 2009) and earlier versions are not affected by this security advisory (disclosed Mar. 2, 2009) because Matomo uses a subset of ZF which does not include Zend_Filter.
Matomo users are, however, encouraged to upgrade to take advantage of new features and bug fixes.
Reference: Cross-site scripting vector in Zend_Filter_StripTags