A critical security vulnerability impacting the
Funnel Builder
plugin for WordPress has come under active exploitation in the wild to
inject malicious JavaScript code
into WooCommerce checkout pages with the goal of stealing payment data.
Details of the activity were
published
by Sansec this week. The vulnerability currently does not have an official CVE identifier. It affects all versions of the plugin before 3.15.0.3. It’s used in more than 40,000 WooCommerce stores.
The flaw lets unauthenticated attackers inject arbitrary JavaScript into every checkout page on the store, the Dutch e-commerce security company said. FunnelKit, which maintains Funnel Builder, has released a patch for the vulnerability in version 3.15.0.3.
“Attackers are planting fake Google Tag Manager scripts into the plugin’s ‘External Scripts’ setting,” it noted. “The injected code looks like ordinary analytics next to the store’s real tags, but loads a payment skimmer that steals credit card numbers, CVVs, and billing addresses from checkout.”
Per Sansec, Funnel Builder includes a publicly exposed checkout endpoint that allows an incoming request to choose the type of internal method to run. However, older versions were designed such that they never checked the caller’s permissions or limited which methods are allowed to be invoked.
A bad actor could exploit this loophole by issuing an unauthenticated request that can reach an unspecified internal method that writes attacker-controlled data directly into the plugin’s global settings. The added code snippet is then injected into every Funnel Builder checkout page.
As a result, an attacker could plant a malicious
