CVE-2025-28939: WP Google Calendar Manager SQLi Flaw

CVE-2025-28939 Overview

CVE-2025-28939 is a Blind SQL Injection vulnerability in the EuroCizia WP Google Calendar Manager plugin (wp-gcalendar) for WordPress. The flaw stems from improper neutralization of special elements used in SQL commands [CWE-89]. It affects all plugin versions up to and including 2.1. An authenticated attacker with low privileges can inject crafted SQL payloads through vulnerable parameters and infer database contents byte by byte. The issue has a changed scope, meaning successful exploitation can impact resources beyond the vulnerable component.

Critical Impact
Authenticated attackers can extract sensitive database contents, including user credentials and WordPress secrets, by abusing time-based or boolean-based blind SQL injection techniques.

Affected Products

EuroCizia WP Google Calendar Manager (wp-gcalendar) plugin versions through 2.1
WordPress installations running the affected plugin
Sites where low-privileged authenticated users can reach the vulnerable endpoint

Discovery Timeline

2025-03-26 - CVE CVE-2025-28939 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-28939

Vulnerability Analysis

The vulnerability resides in the wp-gcalendar plugin, which manages Google Calendar integrations within WordPress. The plugin accepts user-supplied input and concatenates it into SQL statements without proper parameterization or sanitization. Because the application does not return verbose database errors, exploitation typically relies on blind techniques, where attackers infer query outcomes from boolean responses or response timing.

The attack requires authentication but only low privileges, making it reachable by subscriber-tier accounts on sites that permit open registration. The scope is changed, indicating that the injected query can access data outside the authorization boundary of the calling user, including the broader WordPress database schema.

Root Cause

The root cause is the absence of prepared statements when constructing SQL queries from request parameters. Input destined for $wpdb queries is interpolated directly into the SQL string rather than passed through $wpdb->prepare() with proper format specifiers. This allows special characters such as single quotes, parentheses, and SQL keywords to alter the query structure.

Attack Vector

An authenticated attacker sends crafted HTTP requests to the vulnerable plugin endpoint with malicious SQL fragments in parameters. Using payloads that produce conditional SLEEP() delays or boolean differences in responses, the attacker enumerates database content one character at a time. The attack proceeds over the network without user interaction. Refer to the Patchstack Vulnerability Report for the disclosure record.

Detection Methods for CVE-2025-28939

Indicators of Compromise

Repeated authenticated requests to wp-gcalendar plugin endpoints containing SQL meta-characters such as ', ", --, UNION, or SLEEP(
Unusual response time patterns from /wp-admin/admin-ajax.php calls tied to the plugin
Spike in queries to wp_users, wp_usermeta, or wp_options tables originating from PHP requests handling calendar parameters
New or anomalous WordPress administrator accounts following suspicious calendar plugin traffic

Detection Strategies

Inspect web server access logs for request parameters bound to the wp-gcalendar plugin containing encoded SQL syntax
Deploy a Web Application Firewall (WAF) rule set that flags blind SQLi signatures including time-based payloads against WordPress endpoints
Enable MySQL general query logging in staging environments to validate whether plugin inputs reach queries without parameterization
Correlate authentication events with subsequent plugin endpoint access by low-privileged accounts

Monitoring Recommendations

Alert on HTTP responses to wp-gcalendar endpoints whose latency exceeds normal baselines, indicating possible SLEEP() injection
Monitor for newly registered low-privileged accounts immediately followed by calendar plugin requests
Track changes to wp_users and wp_options tables outside normal administrative workflows

How to Mitigate CVE-2025-28939

Immediate Actions Required

Deactivate the WP Google Calendar Manager plugin until a vendor patch is verified and applied
Restrict new user registration or require administrator approval to limit the pool of authenticated attackers
Apply WAF virtual patches blocking SQL injection payloads targeting wp-gcalendar request parameters
Audit WordPress accounts and rotate credentials, secret keys, and API tokens stored in wp_options

Patch Information

At the time of NVD publication, no fixed version above 2.1 is referenced. Site administrators should consult the Patchstack Vulnerability Report for the latest remediation status and any vendor-issued updates.

Workarounds

Remove the wp-gcalendar plugin directory from wp-content/plugins/ if the calendar functionality is non-essential
Place the WordPress admin and AJAX endpoints behind IP allowlisting where feasible
Enforce least privilege by demoting unnecessary contributor or author accounts to subscriber
Enable database user separation so the WordPress database account cannot read sensitive cross-application tables

bash

# Disable the vulnerable plugin via WP-CLI
wp plugin deactivate wp-gcalendar
wp plugin delete wp-gcalendar

# Rotate WordPress salts after suspected compromise
wp config shuffle-salts