CVE-2024-4787 is an improper input validation vulnerability (CWE-20) found in the Cost Calculator Builder PRO plugin for WordPress, developed by StylemixThemes. The flaw exists in the 'send_pdf' and 'send_pdf_front' functions, which are accessible via AJAX endpoints. These functions handle sending emails containing PDF attachments generated by the plugin. Due to insufficient restrictions on the email recipient fields and email content parameters, an unauthenticated attacker can craft requests that cause the plugin to send emails to arbitrary recipients with arbitrary content. This can be exploited remotely without any authentication or user interaction, making it a network-exploitable vulnerability. The vulnerability affects all versions up to and including 3.1.75. While the vulnerability does not allow direct access to sensitive data or system compromise, it undermines the integrity of email communications by enabling spoofed or malicious emails to be sent from the affected WordPress site. This can facilitate phishing, spam campaigns, or reputational damage to the organization hosting the vulnerable plugin. No patches or fixes are currently linked, and no known exploits have been reported in the wild as of the publication date. The CVSS v3.1 base score is 5.8, indicating a medium severity level, with attack vector network (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), and scope changed (S:C).

The primary impact of CVE-2024-4787 is on the integrity of email communications sent from affected WordPress sites. Attackers can abuse the plugin to send arbitrary emails to any recipient, potentially leading to phishing attacks, spam distribution, or social engineering campaigns that appear to originate from a legitimate source. This can damage the reputation of the affected organization and erode trust with customers or partners. Although confidentiality and availability are not directly impacted, the misuse of email functionality can indirectly lead to further attacks if recipients are deceived by malicious content. Organizations relying on this plugin for cost calculations and customer communications may face increased risk of email abuse and associated operational disruptions. The vulnerability's ease of exploitation and unauthenticated access increase the likelihood of exploitation attempts, especially on publicly accessible WordPress sites. The scope is broad since all versions up to 3.1.75 are affected, and the plugin is used globally in various industries, including e-commerce, services, and consulting.

1. Immediately update the Cost Calculator Builder PRO plugin to a patched version once available from StylemixThemes. Monitor official channels for release announcements. 2. In the absence of an official patch, implement web application firewall (WAF) rules to block or restrict access to the vulnerable AJAX endpoints ('send_pdf' and 'send_pdf_front'). 3. Restrict outgoing SMTP email permissions on the web server to prevent unauthorized email sending or configure rate limiting to detect and block abnormal email volumes. 4. Review and harden email sending configurations in WordPress and the plugin settings to limit allowed recipient domains or addresses. 5. Monitor email logs for unusual sending patterns or unauthorized emails originating from the affected site. 6. Educate staff and users about potential phishing risks stemming from this vulnerability. 7. Consider disabling the PDF email sending feature temporarily if it is not critical to operations until a patch is applied. 8. Conduct regular vulnerability scans and penetration tests to detect similar input validation issues in other plugins or custom code.