Pannellum is a lightweight, free, and open source panorama viewer for the web. In versions 3.5.0 through 2.5.6, the hot spot attributes configuration property allowed any attribute to be set, including HTML event handler attributes, allowing for potential XSS attacks. This affects websites hosting the standalone viewer HTML file and any other use of untrusted JSON config files (bypassing the protections of the escapeHTML parameter). As certain events fire without any additional user interaction, visiting a standalone viewer URL that points to a malicious config file — without additional user interaction — is sufficient to trigger the vulnerability and execute arbitrary JavaScript code, which can, for example, replace the contents of the page with arbitrary content and make it appear to be hosted by the website hosting the standalone viewer HTML file. This issue has been fixed in version 2.5.7. To workaround, setting the Content-Security-Policy header to script-src-attr 'none' will block execution of inline event handlers, mitigating this vulnerability. Don't host pannellum.htm on a domain that shares cookies with user authentication to mitigate XSS risk.

In Pannellum from 2.5.0 through 2.5.4 URLs were not sanitized for data URIs (or vbscript:), allowing for potential XSS attacks. Such an attack would require a user to click on a hot spot to execute and would require an attacker-provided configuration. The most plausible potential attack would be if pannellum.htm was hosted on a domain that shared cookies with the targeted site's user authentication; an <iframe> could then be embedded on the attacker's site using pannellum.htm from the targeted site, which would allow the attacker to potentially access information from the targeted site as the authenticated user (or worse if the targeted site did not have adequate CSRF protections) if the user clicked on a hot spot in the attacker's embedded panorama viewer. This was patched in version 2.5.5.