CVE-2026-57418: Sprout Invoices Auth Bypass Vulnerability

CVE-2026-57418 Overview

CVE-2026-57418 is a Missing Authorization vulnerability [CWE-862] in the BoldGrid Client Invoicing by Sprout Invoices WordPress plugin. The flaw affects all plugin versions up to and including 20.8.13. Authenticated attackers with low privileges can exploit incorrectly configured access control security levels to reach functionality that should be restricted. The vulnerability requires network access and low attack complexity, and it impacts the confidentiality of data managed by the plugin. Successful exploitation exposes invoicing data without requiring user interaction.

Critical Impact
Authenticated low-privilege users can bypass access control checks in Sprout Invoices, exposing confidential invoicing information stored in WordPress.

Affected Products

BoldGrid Client Invoicing by Sprout Invoices (sprout-invoices) WordPress plugin
All versions from n/a through 20.8.13
WordPress sites running the vulnerable plugin

Discovery Timeline

2026-07-13 - CVE-2026-57418 published to NVD
2026-07-13 - Last updated in NVD database

Technical Details for CVE-2026-57418

Vulnerability Analysis

The vulnerability stems from a broken access control implementation within the Sprout Invoices plugin. Plugin endpoints fail to enforce capability checks that verify whether the requesting user is authorized to perform the requested action. An authenticated attacker with a low-privilege WordPress role can invoke protected functionality by sending crafted requests to the plugin's exposed handlers. The impact is limited to confidentiality, allowing exposure of invoicing records, client information, and related billing artifacts managed by the plugin. Integrity and availability are not affected according to the published scoring vector.

Root Cause

The root cause is a missing authorization check [CWE-862] on plugin actions. The code path does not validate the current user's role or capabilities through WordPress functions such as current_user_can() before executing sensitive operations. This design flaw permits access from any authenticated context, including subscriber-level accounts that should have no administrative reach into invoicing data.

Attack Vector

Exploitation occurs over the network against the WordPress admin-ajax or REST endpoints exposed by the plugin. The attacker must hold a valid low-privilege session on the target site. No user interaction is required, and the request payload leverages the plugin's own action handlers to retrieve or interact with protected invoicing resources.

No public proof-of-concept has been released. For technical details, see the Patchstack Vulnerability Analysis.

Detection Methods for CVE-2026-57418

Indicators of Compromise

Unexpected access to admin-ajax.php or REST endpoints containing the sprout-invoices or si_ action parameters from low-privilege accounts.
Anomalous invoice, estimate, or client record enumeration in plugin logs and WordPress audit trails.
Requests from subscriber or customer role sessions accessing invoicing data outside their scope.

Detection Strategies

Review WordPress access logs for high-volume requests to Sprout Invoices AJAX or REST routes from non-administrative users.
Correlate authentication events with plugin activity to identify low-privilege sessions triggering invoicing operations.
Deploy a WordPress security plugin or web application firewall rule that inspects action parameters targeting sprout-invoices handlers.

Monitoring Recommendations

Enable verbose logging on WordPress and forward events to a centralized log platform for retention and correlation.
Alert on newly registered low-privilege accounts followed by plugin endpoint activity within a short interval.
Track outbound data volumes from the site to identify bulk exfiltration of invoicing records.

How to Mitigate CVE-2026-57418

Immediate Actions Required

Update the Sprout Invoices plugin to a version released after 20.8.13 as soon as the vendor publishes a fix.
Audit existing WordPress user accounts and remove or suspend unnecessary low-privilege accounts.
Restrict new user registration on public-facing WordPress sites where invoicing data is stored.

Patch Information

At the time of publication, the advisory covers all versions of Client Invoicing by Sprout Invoices through 20.8.13. Site owners should monitor the Patchstack advisory and the WordPress plugin repository for the patched release, and apply it immediately upon availability.

Workarounds

Temporarily disable the Sprout Invoices plugin on sites that do not require active invoicing functionality until a patched version is deployed.
Deploy a web application firewall rule that blocks unauthenticated and low-privilege requests to plugin-specific AJAX and REST actions.
Enforce least privilege on WordPress roles and remove any custom capability grants that expose plugin endpoints to non-administrative users.

bash

# Example WAF rule concept to block low-privilege access to plugin actions
# Adjust for your WAF syntax (ModSecurity example)
SecRule REQUEST_URI "@rx /wp-admin/admin-ajax\.php" \
  "chain,deny,status:403,id:1002026574,msg:'Block Sprout Invoices action from non-admin'"
SecRule ARGS:action "@rx ^(sprout_invoices|si_)" \
  "chain"
SecRule &SESSION:is_admin "@eq 0"