Executive Summary

[{'type': 'paragraph', 'content': "The CallbackKiller service widget plugin for WordPress has a vulnerability due to a missing capability check in its cbk_save() function. This flaw exists in all versions up to and including 1.2. Because of this, unauthenticated attackers can exploit the 'cbk_save_v1' AJAX action to modify the plugin's site ID settings without authorization."}, {'type': 'paragraph', 'content': 'The plugin exposes several AJAX actions that are accessible to both logged-in and non-logged-in users, including signin, signup, signout, and save. The cbk_save() function, responsible for updating the site ID, lacks proper permission checks, allowing attackers to change site configuration remotely. Additionally, the plugin does not sanitize user input and communicates with its API over insecure HTTP, which further weakens its security posture.'}] [1]

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Impact Analysis

This vulnerability allows unauthenticated attackers to modify the site ID settings of the CallbackKiller plugin on a WordPress site. While it does not directly impact confidentiality or availability, it compromises the integrity of the plugin's configuration.

An attacker could manipulate the plugin's settings to redirect or interfere with the callback and chat service functionality, potentially disrupting legitimate communications or redirecting callbacks to malicious endpoints. This could lead to loss of trust, service disruption, or unauthorized control over certain plugin behaviors.

The CVSS v3.1 base score of 5.3 reflects a medium severity impact, indicating that the vulnerability is exploitable remotely without authentication but does not affect confidentiality or availability.

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Compliance Impact

I don't know

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Detection Guidance

[{'type': 'paragraph', 'content': "This vulnerability can be detected by monitoring for unauthorized AJAX requests to the 'cbk_save_v1' action on WordPress sites using the CallbackKiller plugin up to version 1.2. Specifically, look for HTTP POST or GET requests targeting the AJAX endpoint with the parameter 'action=cbk_save_v1' coming from unauthenticated sources."}, {'type': 'paragraph', 'content': 'You can use network monitoring or web server access logs to identify such requests. For example, using command line tools on the server hosting the WordPress site:'}, {'type': 'list_item', 'content': "Use grep to search web server logs for suspicious AJAX calls: grep 'action=cbk_save_v1' /var/log/apache2/access.log"}, {'type': 'list_item', 'content': "Use curl to manually test if the AJAX action is accessible without authentication: curl -X POST 'https://yourwordpresssite.com/wp-admin/admin-ajax.php?action=cbk_save_v1' -d 'site_id=malicious_value'"}, {'type': 'list_item', 'content': "Use tools like Wireshark or tcpdump to capture HTTP traffic and filter for requests containing 'cbk_save_v1'."}] [1]

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Mitigation Strategies

[{'type': 'paragraph', 'content': 'Immediate mitigation steps include:'}, {'type': 'list_item', 'content': 'Disable or remove the CallbackKiller plugin until a patched version is available.'}, {'type': 'list_item', 'content': "Restrict access to the WordPress AJAX endpoint (admin-ajax.php) to authenticated users only, or block unauthenticated requests to the 'cbk_save_v1' action."}, {'type': 'list_item', 'content': 'Implement web application firewall (WAF) rules to detect and block unauthorized AJAX requests targeting this plugin.'}, {'type': 'list_item', 'content': "Monitor and audit WordPress options related to the plugin (such as 'cbk_site_id') for unauthorized changes."}, {'type': 'list_item', 'content': 'Apply the latest updates or patches from the plugin developer once available.'}] [1]

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