Vulnerability · Published Jul 18, 2026 · Assigned by VulnCheck

CVE-2026-57857Flow Payment Plugin for WordPress Reflected Cross-Site Scripting via error_message Parameter

Medium 4.3

In plain English

A medium-severity cross-site scripting in Flow Payment from Flow. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 27% of all known vulnerabilities).

Severity (CVSS 3.1)4.3Medium

Exploit odds (30 days)0.3%top 72.9% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

The Flow Payment plugin for WordPress (flow.cl) version 3.0.8 is vulnerable to reflected cross-site scripting on the WooCommerce checkout page. When the plugin handles an order cancellation, the error_message GET parameter is passed directly to wc_add_notice() in flowpayment-fl.php (lines 57-58) without input sanitization (for example sanitize_text_field()) or output escaping (for example esc_html()) before being rendered in the checkout notice HTML. An unauthenticated attacker can craft a URL containing a JavaScript payload in the error_message parameter (for example /checkout/?add-to-cart={product-id}&cancel_order=true&error_message={payload}); when a victim with an active WooCommerce checkout session follows the link, the payload executes in the victim's browser in the origin of the WordPress site.

Affected products (as reported)

Vendor	Product	Versions
Flow	Flow Payment	0 – through 3.0.8

Weakness: CWE-79 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

References

Vendor Website product
https://www.vulncheck.com/advisories/flow-payment-plugin-for-wordpress-reflected-cross-site-scripting-via-error-message-parameter third-party-advisory