Introduction: What is a PPTX File?

Modern PowerPoint files – those using the .pptx extension – are based on the Open Office XML standard introduced in 2007. Instead of the binary containers all MS Office documents once were, PPTX files are compressed ZIP archives composed of XML files and media directories. These files define each and every slide, text box, image, animation, and hyperlink we see when we open a PowerPoint document. It’s very much so a literal ZIP file we’re talking about here; you can actually extract a PPTX file (and any other Open Office XML file type) by renaming it with a .zip extension and unzipping its contents the same way you would with any ZIP folder.

PowerPoint’s XML format follows a modular format, which makes it much easier to organize rich content – including everything from text to audio, video, embedded objects, and scripts. While this structure does support productivity and presentation design, it also provides threat actors with a layered playground to hide threats within. Getting hacked by specially crafted PPTX documents is a real possibility, and it’s one we need to actively defend our system against.

In this article, we’ll discuss what makes PPTX files a target in more detail. We’ll look at an example of how PowerPoints have been weaponized in the past, and we’ll learn how Cloudmersive’s Advanced Virus Scan API identifies insecure content in PPTX files with deep content verification.

Why PPTX Files are a Worthy Threat Vector

MS Office files like PPTX have the advantage of appearing harmless to everyday users in an enterprise system. It’s not just that they’re an extremely common file type – it’s also that they’re not Excel XLSX or XLSM documents, which are more widely feared for their involvement in large-scale attack campaigns.
PPTX files are regularly exchanged in corporate settings, emailed between coworkers, and uploaded to SharePoint or Teams without a second thought. The file structure supports embedding links to external media, OLE Objects, and advanced transitions – all of which can be manipulated to trigger execution of remote or malicious content.

Files with advanced dynamic features that are shared everywhere and inspected infrequently represent strong threat vectors. When we combine user behavior into this equation (e.g., enabling content, clicking links, or trusting shared drives), PPTX files become an exceptionally low-friction opportunity to compromise endpoints.

Attack Surface: What can be Embedded in a PowerPoint?

Below, we'll take a closer look at the embedded or linked content that may pose a risk in any given PPTX file. Threat actors can combine several of these elements to create files which look polished and quietly trigger malicious behavior once they’re opened.

Linked OLE Objects

Like other OOXML documents, PPTX files can reference outside files – and that includes executables or scripts. The object path can be weaponized in a PowerPoint, pointing users to a malicious payload on a remote server.

Hyperlinks

Uniform Resource Locators (URLs) show up everywhere in modern enterprise documents, and they can point anywhere the document creator wants them to. In a specially crafted PPTX, these can point users to credential phishing pages and even initiate malware downloads.

Macros

PPTX doesn’t support VBA macros natively, but threat actors can still link scripts within a PPTX file or link external documents which contain macro-enabled content themselves.

ActiveX Controls

ActiveX controls can be embedded in older versions of Office or used as part of an OLE package. This is much more rare, but it’s still worth bearing in mind.

Embedded Media Files

PowerPoint supports all kinds of different media files, and each of those can carry its own risks. Video files like MP4, Flash, or WMV can contain exploits when played through vulnerable media engines, and image files can disguise malware in their pixel data.

PPTX Exploits in the Wild: CVE-2017-8570

CVE-2017-8570 was a vulnerability exploited with PPTX and DOCX files. Attackers could embed malicious OLE objects referencing an external .HTA file (HTML Application) which downloaded and ran malware on the victim’s device. While this CVE primarily affected DOC-based vectors (and is a bit old by CVE standards), it’s a great example of how easily the OOXML file structure can be manipulated to point to insecure content.

Detecting Malicious PPTX Files with Cloudmersive

Cloudmersive’s Advanced Virus Scan API takes a multi-layered approach to detecting threats in files like PPTX. This involves deep content verification and traditional malware signature scanning.

The API first ensures the contents of any file bearing the .pptx extension rigorously conform with PowerPoint formatting standards. This addresses invalid PPTX files which may be used to exploit vulnerabilities in weakly configured file parsers.

Beyond that, it unpacks the ZIP structure of PPTX files and analyzes each internal component – including all links and objects – for malicious content. Signature-based scanning (referencing a database of 17 million+ virus and malware signatures) identifies directly traceable malware, and heuristic & behavioral analysis identifies malicious behaviors.

The Advanced Scan API can be integrated directly with individual web applications with minimal code changes, or deployed as a no-code solution in several of Cloudmersive’s enterprise grade products (such as Storage Protect, Shield, and the AI Web Application Firewall).

Final Thoughts

PowerPoints are much more than slide decks. Their complex format and trusted role in enterprise business environments makes them a quiet and powerful attack vector. Understanding the way PPTX files are structured (and how threat actors abuse this structure) is critical for designing secure file upload & transfer systems, email filters, and regular document processing workflows.

To learn more about defending against PPTX threats with Cloudmersive’s Advanced Virus Scan API, please contact a member of our team.