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.

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.

The Piwik_Common::getIP function in Piwik before 1.1 does not properly determine the client IP address, which allows remote attackers to bypass intended geolocation and logging functionality via (1) use of a private (aka RFC 1918) address behind a proxy server or (2) spoofing of the X-Forwarded-For HTTP header.

Multiple cross-site scripting (XSS) vulnerabilities in Piwik before 1.1 allow remote attackers to inject arbitrary web script or HTML via unspecified vectors.

Cross-site scripting (XSS) vulnerability in the Login form in Piwik 0.1.6 through 0.5.5 allows remote attackers to inject arbitrary web script or HTML via the form_url parameter.