A newly uncovered security vulnerability in Microsoft Office Word has raised concerns regarding the security of this widely used productivity suite.
This security flaw has been categorized as a Cross-Site Scripting (XSS) vulnerability, which allows malicious actors to execute arbitrary JavaScript code within a Word document. This XSS vulnerability affects various Office products, including Microsoft Word, and revolves around a feature that permits users to embed external videos in documents through the “Online Videos” tab.
When a user attempts to play an external video embedded within a document, Office conducts a check to ascertain the trustworthiness of the video’s source. This evaluation involves the application of a regular expression to the video’s URL, which includes well-known sources like YouTube. If the source is considered reliable, Office requests data such as the video’s title or thumbnail. However, the vulnerability arises from how Office manages the video’s title within the HTML iframe tag.
The server responds with information, including the video’s title, description, and the HTML iframe tag. The problem arises when the server incorporates the video’s title into the “title” attribute of the iframe tag without proper validation. This oversight allows attackers to manipulate the iframe tag by introducing an “unload” attribute, thereby enabling them to inject arbitrary JavaScript code.
Exploiting this vulnerability involves several steps. Attackers create a YouTube video with a title containing a payload designed to insert the “onload” attribute. They then insert the URL of this malicious video into a Word document using the Online Videos tab. When the video is played, the injected JavaScript code is executed.
The consequences of this vulnerability are significant. Attackers can execute arbitrary JavaScript code when a video embedded in a Word document is played. While this may not appear immediately alarming, it’s essential to note that past critical exploits in Office applications often began with the execution of arbitrary JavaScript. If combined with a new vulnerable Uniform Resource Identifier (URI), exploiting this vulnerability could potentially lead to a critical Remote Code Execution (RCE) vulnerability.
This underscores the urgency for Microsoft to address and patch this issue promptly. The Microsoft Office XSS flaw emphasizes the importance of maintaining up-to-date software and exercising caution when dealing with content embedded in documents. Users should be vigilant about potential security risks associated with video content, particularly when it originates from untrusted sources.