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. 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 . This product uses the NVD API but is not endorsed or certified by the NVD.