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Cross-site Scripting occurrences in Tinymce
tinymce is an open source rich text editor. A cross-site scripting (XSS) vulnerability was discovered in the alert and confirm dialogs when these dialogs were provided with malicious HTML content. This can occur in plugins that use the alert or confirm dialogs, such as in the `image` plugin, which presents these dialogs when certain errors occur. The vulnerability allowed arbitrary JavaScript execution when an alert presented in the TinyMCE UI for the current user. This vulnerability has been patched in TinyMCE 5.10.7 and TinyMCE 6.3.1 by ensuring HTML sanitization was still performed after unwrapping invalid elements. Users are advised to upgrade to either 5.10.7 or 6.3.1. Users unable to upgrade may ensure the the `images_upload_handler` returns a valid value as per the images_upload_handler documentation. (2022-12-08, CVE-2022-23494)
A cross-site scripting (XSS) vulnerability in TinyMCE 5.2.1 and earlier allows remote attackers to inject arbitrary web script when configured in classic editing mode. (2020-08-14, CVE-2020-12648)
TinyMCE before 4.9.7 and 5.x before 5.1.4 allows XSS in the core parser, the paste plugin, and the visualchars plugin by using the clipboard or APIs to insert content into the editor. (2020-08-10, CVE-2020-17480)
tinymce 4.7.11, 4.7.12 is affected by: CWE-79: Improper Neutralization of Input During Web Page Generation. The impact is: JavaScript code execution. The component is: Media element. The attack vector is: The victim must paste malicious content to media element's embed tab. (2019-07-17, CVE-2019-1010091)
Why Cross-site Scripting can be dangerous
Cross site scripting is an attack where a web page executes code that is injected by an adversary. It usually appears, when users input is presented. This attack can be used to impersonate a user, take over control of the session, or even steal API keys.
The attack can be executed e.g. when you application injects the request parameter directly into the HTML code of the page returned to the user:
https://server.com/confirmation?message=Transaction+Complete
what results in:
<span>Confirmation: Transaction Complete</span>
In that case the message can be modified to become a valid Javascript code, e.g.:
https://server.com/confirmation?message=<script>dangerous javascript code here</script>
and it will be executed locally by the user's browser with full access to the user's personal application/browser data:
<span>Confirmation: <script>dangerous javascript code here</script></span>