CVE-2026-57857 Flow Payment Plugin for WordPress Reflected Cross-Site Scripting via error_message Parameter
An unauthenticated attacker can execute arbitrary JavaScript in a victim's browser via a crafted URL on the WooCommerce checkout page.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-57857?
CVE-2026-57857 is a medium-severity cross-site scripting vulnerability in Flow Payment, published on 18 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
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.
Weakness: CWE-79
Which versions are affected by CVE-2026-57857?
How do I fix CVE-2026-57857?
No fix has been published for CVE-2026-57857 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-57857 being exploited?
There is no known exploitation of CVE-2026-57857 in the wild and no public exploit code.
Sources
Also known as GHSA-r6hg-r245-924g.