CVE-2026-91788 in PDF Editor
Summary
by MITRE • 09/23/2026
When implementing the JavaScript interface, Foxit PDF Editor/Reader did not perform the attribute authorization checks required by the specification. As a result, a trusted malicious PDF could potentially access sensitive content from other documents within the same process and transmit it externally.
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Analysis
by VulDB Data Team • 09/23/2026
The vulnerability in question stems from an improper implementation of security controls within the JavaScript interface of Foxit PDF Editor and Reader applications. Specifically, the software fails to enforce attribute authorization checks that are mandated by the relevant technical specifications for secure document processing environments. This deficiency represents a fundamental breakdown in the principle of least privilege and isolation boundaries between different components or documents operating within the same application instance. In modern web-based and embedded scripting engines used in PDF readers, JavaScript execution contexts must be strictly sandboxed to prevent cross-document interference. The absence of these checks means that the runtime environment does not adequately verify whether a script executing from one document has legitimate permission to interact with resources belonging to another document loaded in the same process space.
From a technical perspective, this flaw allows for what is known as Cross-Document Scripting or unauthorized resource access within a single-process architecture. When a malicious PDF file containing crafted JavaScript code is opened by an unsuspecting user, the embedded script can exploit the missing authorization logic to reach out and read attributes, content, or metadata from other open documents in the same Foxit instance. This capability bypasses standard security boundaries that are typically enforced at the browser engine level for web pages but were not correctly replicated or configured within the PDF reader's internal JavaScript sandbox. The attacker can programmatically traverse the document object model of sibling windows or tabs to extract sensitive information such as personal data, financial records, or proprietary business documents currently open in the application.
The operational impact of this vulnerability is severe due to its potential for silent data exfiltration. Once a malicious PDF gains access to the content of other trusted documents within the same process, it can construct HTTP requests or use other network capabilities inherent in the JavaScript environment to transmit that stolen data to an external server controlled by the attacker. This scenario effectively turns the user's own workstation into a vector for espionage and intellectual property theft without requiring additional exploits like buffer overflows or arbitrary code execution. The victim may remain unaware of the breach because the malicious PDF appears benign, and the application continues to function normally while silently leaking sensitive information in the background.
This vulnerability aligns with CWE-284 Improper Access Control, as it involves a failure to restrict access to resources based on user identity or trust level within an application context. It also maps closely to MITRE ATT&CK techniques related to Data from Local System and potentially Command and Scripting Interpreter if the JavaScript is used to chain further attacks. The lack of proper isolation between documents loaded in the same process space violates fundamental security design principles that require strict separation of contexts to prevent lateral movement within an application's memory space.
Mitigation strategies must focus on both immediate remediation and long-term architectural improvements. Users should immediately update Foxit PDF Editor or Reader to the latest version where this authorization check has been implemented by the vendor. Until patches are applied, it is advisable to disable JavaScript execution entirely for untrusted documents through application settings if such an option exists in older versions. Furthermore, organizations should enforce strict policies regarding which users can open external PDF files and consider using isolated environments or virtual machines for processing sensitive documents from unknown sources. Developers must ensure that future implementations of the JavaScript engine strictly adhere to specification requirements by implementing robust origin checks and permission validation before allowing any inter-document communication or resource access.