Media Embed XSS in Plate Editor via Unsafe URL Handling

Executive Summary

This vulnerability exists in the Plate rich-text editor versions from 53.0.0 up to 53.1.4. The issue arises because the media embed renderer trusts serialized provider or sourceUrl metadata without properly validating the protocol of the media URL. Specifically, it skips the parseMediaUrl protocol validation, which allows an attacker to craft a Plate document that sets a known video provider but uses a javascript: iframe source URL. When a victim opens this document, the MediaEmbedElement registry renders this malicious iframe source directly, potentially leading to execution of malicious scripts.

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Impact Analysis

This vulnerability can have serious security impacts. Because the media embed renderer can be tricked into rendering a malicious iframe with a javascript: URL, it can lead to cross-site scripting (XSS) attacks. This means an attacker could execute arbitrary scripts in the context of the victim's browser when they open the crafted document. The CVSS score of 8.7 indicates a high severity with potential for high confidentiality and integrity impact, although availability is not affected.

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Mitigation Strategies

To mitigate this vulnerability, update the Plate rich-text editor to version 53.1.4 or later, where the issue is fixed.

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Compliance Impact

The vulnerability allows execution of malicious JavaScript in the victim's browser by bypassing media embed URL sanitization, potentially exposing application data and enabling unauthorized actions on behalf of the victim.

Such unauthorized data exposure and execution of malicious code could lead to non-compliance with data protection regulations like GDPR and HIPAA, which require safeguarding personal and sensitive information against unauthorized access and ensuring application security.

However, the provided context and resources do not explicitly discuss the impact of this vulnerability on compliance with specific standards or regulations.

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Detection Guidance

This vulnerability involves the Plate rich-text editor rendering malicious iframe URLs embedded in serialized provider or sourceUrl metadata. Detection would focus on identifying documents or data containing iframe URLs with javascript: protocols or other suspicious URL schemes that bypass protocol validation.

Since the issue arises from unsafe serialized iframe URLs in Plate documents, you can detect potential exploitation by searching for such patterns in your stored documents or network traffic.

• Use grep or similar tools to scan stored Plate documents or serialized data for iframe src attributes containing 'javascript:' URLs, e.g.: grep -r "iframe.*src=['"]javascript:" /path/to/documents
• Monitor network traffic for HTTP requests or WebSocket messages carrying Plate documents or media embed data containing suspicious iframe URLs with javascript: schemes.
• If you have access to the application logs or database, query for entries where media embed metadata fields like provider or sourceUrl contain 'javascript:' or other non-standard protocols.

No specific detection commands are provided in the available resources, but these general approaches can help identify exploitation attempts.

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