Attack Chain

1. An unauthenticated attacker crafts a malicious HTTP GET or POST request targeting a WordPress site running the Ultimate Member plugin.
2. The crafted request includes SQL injection payloads within the search parameter (e.g., ?search=test%27%20AND%20SLEEP(5)--%20 or ?search=admin%27%20OR%201=1--%20).
3. Due to inadequate input sanitization and lack of parameterized queries within the plugin's code, the malicious input from the search parameter is directly incorporated into a backend SQL query.
4. The injected blind SQL query executes on the database server, causing a differential response, such as a time delay for time-based attacks or a distinct content change for boolean-based attacks.
5. The attacker analyzes the web server's response (e.g., HTTP response time, page content) to infer the result of the injected SQL condition.
6. The attacker iteratively sends numerous such requests, modifying the payload in the search parameter to extract sensitive data, character by character, or by evaluating true/false conditions.
7. Sensitive information, such as user credentials, API keys, or private configuration data, is systematically exfiltrated from the WordPress database.

Impact

The successful exploitation of CVE-2026-15290 allows unauthenticated attackers to extract sensitive data from the WordPress database. This could lead to a compromise of user accounts, administrative credentials, and other confidential information stored within the system. The stolen data could then be used for further attacks, identity theft, or sold on illicit markets, leading to severe financial, reputational, and operational damage for affected organizations. The vulnerability's high CVSS v3.1 score of 7.5 reflects the significant risk posed by unauthorized data disclosure without any prior authentication required.

Recommendation

• Immediately update the Ultimate Member plugin for WordPress to a version patched against CVE-2026-15290 (versions higher than 2.10.1).
• Deploy the Sigma rule Detect Blind SQL Injection Attempts in Ultimate Member Plugin to your SIEM to identify and alert on potential exploitation attempts via the search parameter.
• Ensure detailed web server access logs are enabled and collected for your WordPress instances, specifically capturing full HTTP request URLs and query parameters.