InstantSoft icms2 Billing paypal.php validatePaypalOrder data authenticity

A vulnerability was determined in InstantSoft icms2 up to 2.18.2. The affected element is the function validatePaypalOrder of the file system/controllers/billing/actions/paypal.php of the component Billing Module. Executing a manipulation of the argument bid/sig can lead to insufficient verification of data authenticity. The attack may be launched remotely. The exploit has been publicly disclosed and may be utilized. The vendor was contacted early about this disclosure but did not respond in any way.