CVE-2020-35489: 
WordPress vulnerability analysis and mitigation

The Contact Form 7 (CF7) plugin versions before 5.3.2 for WordPress contained an Unrestricted File Upload vulnerability (CVE-2020-35489), discovered in December 2020. The vulnerability allowed attackers to bypass filename sanitization and upload files that could be executed as scripts on the host server. This critical vulnerability affected over 5 million active WordPress installations that were using Contact Form 7 (Vendor Advisory, WPScan).

The vulnerability received a CVSS v3.1 Base Score of 10.0 (CRITICAL) with the vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H. The vulnerability stemmed from improper filename sanitization, where special characters (Unicode characters from U+0000 [null] to U+001F) could be appended to filenames, bypassing the plugin's security restrictions (Jinson Blog).

The vulnerability allowed attackers to upload malicious files that could be executed as scripts on the host server, potentially leading to remote code execution. Given Contact Form 7's massive user base of over 5 million active installations, the potential impact was significant, putting numerous WordPress websites at risk of complete compromise (WPScan).

The vulnerability was patched in Contact Form 7 version 5.3.2, released on December 17, 2020. The primary mitigation was to update to this version or later immediately. Users with web application firewalls were also protected against exploitation. The fix involved improving the filename sanitization process to prevent bypass using special characters (Vendor Advisory).

The Contact Form 7 plugin developer, Takayuki Miyoshi, responded quickly to the vulnerability report and released a patch within 24 hours of notification, demonstrating responsible handling of the security issue. The security community praised the quick response while expressing concern about the large number of WordPress websites still running older versions (Jinson Blog).