CVE-2020-12648: 
JavaScript vulnerability analysis and mitigation

A cross-site scripting (XSS) vulnerability was discovered in TinyMCE version 5.2.1 and earlier, identified as CVE-2020-12648. TinyMCE is a popular WYSIWYG HTML editor used in content management systems of websites, with reported downloads of 350 million times per year and inclusion in more than 100 million websites. The vulnerability was discovered in April 2020 and was patched in July 2020 (SecurityWeek, Threatpost).

The vulnerability occurs when TinyMCE is configured in classic editing mode, where content is not correctly sanitized before being loaded into the editor. Attackers can bypass the built-in sanitization measures by using nested and non-terminated HTML tags, allowing them to inject an img tag with arbitrary src and onerror values. The vulnerability can be triggered through the setContent() or insertContent() functions when a crafted payload is processed (Bishop Fox).

The severity of this vulnerability varies depending on the implementation, but it could potentially lead to privilege escalation, sensitive information disclosure, and account takeover. In specific scenarios, attackers could execute arbitrary code within the context of the administrative session, potentially gaining administrative privileges to websites (Threatpost).

The vulnerability was patched in TinyMCE versions 4.9.11 (released July 13, 2020) and 5.4.1 (released July 8, 2020). Users are recommended to upgrade to the latest version, particularly version 5.4.1 as version 4 reached end-of-life in December 2020. Additional mitigation strategies include implementing server-side content sanitization and adding a suitable Content Security Policy (CSP) to websites (Threatpost).