Piwik before 1.1 does not prevent the rendering of the login form inside a frame in a third-party HTML document, which makes it easier for remote attackers to conduct clickjacking attacks via a crafted web site.
Cookie.php in Piwik before 1.1 does not set the secure flag for the session cookie in an https session, which makes it easier for remote attackers to capture this cookie by intercepting its transmission within an http session.
Piwik before 1.1 does not properly limit the number of files stored under tmp/sessions/, which might allow remote attackers to cause a denial of service (inode consumption) by establishing many sessions.
Unrestricted file upload vulnerability in ofc_upload_image.php in Open Flash Chart v2 Beta 1 through v2 Lug Wyrm Charmer, as used in Piwik 0.2.35 through 0.4.3, Woopra Analytics Plugin before 1.4.3.2, and possibly other products, when register_globals is enabled, allows remote authenticated users to execute arbitrary code by uploading a file with an executable extension through the name parameter with the code in the HTTP_RAW_POST_DATA parameter, then accessing it via a direct request to the file in tmp-upload-images/.