# CVE-2026-57857 — Flow Payment

> As of 2026-07-18, CVE-2026-57857 is a MEDIUM-severity vulnerability in Flow Payment, CVSS v3.1 4.3, EPSS 0.2% (13.0th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-57857 as of 2026-07-18; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-07-18

## What is CVE-2026-57857?

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.

The record classifies CVE-2026-57857 under weakness class [CWE-79](https://intel.threadlinqs.com/cwe/CWE-79). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs a user to take an action first. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 79 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 4.3 — MEDIUM (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N`)
- **CVSS v4.0 base score:** 5.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **EPSS (FIRST):** 0.2% probability of exploitation in the next 30 days, higher than 13.0% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 2.7/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-07-18

## Is CVE-2026-57857 being exploited?

It currently carries a trending score of 33 in the Threadlinqs vulnerability feed.

## Affected products and versions

- **Flow**: Payment

## How to fix CVE-2026-57857

No vendor patch reference has been recorded for CVE-2026-57857 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-57857

No threat campaign in the Threadlinqs corpus currently references CVE-2026-57857, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories. Last verified by Threadlinqs on 2026-07-20. This product uses the NVD API but is not endorsed or certified by the NVD.

**Third-party advisory**

- [vulncheck.com — third party advisory](https://www.vulncheck.com/advisories/flow-payment-plugin-for-wordpress-reflected-cross-site-scripting-via-error-message-parameter)

**Issue tracking and product pages**

- [flow.cl — product](https://www.flow.cl/)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-57857
Full detection coverage and IOCs for threats exploiting CVE-2026-57857 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp