Piwik -- remote command execution vulnerability

The Piwik security advisory reports:

The Piwik 1.5 release addresses a critical security vulnerability, which affect all Piwik users that have let granted some access to the "anonymous" user.

Piwik contains a remotely exploitable vulnerability that could allow a remote attacker to execute arbitrary code. Only installations that have granted untrusted view access to their stats (ie. grant "view" access to a website to anonymous) are at risk.

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