CVE-2026-106559 in Backstage
Summary
by MITRE • 10/07/2026
Backstage is an open framework for building developer portals. Prior to 0.3.25, the @backstage/plugin-scaffolder-backend-module-confluence-to-markdown package is affected by improper input validation in confluence to markdown scaffolder module. Insufficient input validation in the Confluence to Markdown scaffolder module could allow an attacker to influence file write operations during template execution. Exploitation requires a Backstage user to run a template that processes attacker-influenced Confluence content. This issue is fixed in version 0.3.25.
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Analysis
by VulDB Data Team • 10/07/2026
The vulnerability identified within the @backstage/plugin-scaffolder-backend-module-confluence-to-markdown package of the Backstage developer portal framework represents a critical failure in input validation mechanisms during template execution. Backstage serves as an open-source platform for constructing internal developer portals, facilitating service cataloging and infrastructure automation through customizable templates. The specific module in question is responsible for converting content from Confluence, a popular enterprise wiki software, into Markdown format to be used within scaffolder templates. Prior to version 0.3.25, this conversion process lacked rigorous sanitization of user-supplied data originating from Confluence pages. This architectural oversight creates a pathway for attackers who possess valid credentials or access to influence the content processed by the system to inject malicious payloads into the resulting Markdown output.
The core technical flaw lies in the improper handling of input data during the transformation phase. When a Backstage template is executed, it often involves writing files to the local file system or generating dynamic code based on provided parameters. Because the Confluence-to-Markdown module did not adequately validate or escape special characters and structural elements within the imported content, an attacker could manipulate this content to include directives that alter standard file write operations. This type of vulnerability is classically categorized under CWE-20 Improper Input Validation, as the system failed to verify whether the input met expected constraints before processing it further downstream in the application logic.
The operational impact of this vulnerability is significant due to its potential for arbitrary file writes and code execution within the context of the Backstage backend service. If an attacker can influence a template that processes their controlled Confluence content, they may achieve remote code execution on the server hosting the scaffolder component. This could lead to full compromise of the underlying infrastructure, allowing the extraction of sensitive data stored in the developer portal or using the compromised node as a pivot point for further network attacks. The exploitation vector requires social engineering or prior access, specifically necessitating that a Backstage user runs a template that processes attacker-influenced Confluence content, which aligns with ATT&CK technique T1059 Command and Scripting Interpreter if script injection is involved, or potentially T1204 User Execution if the attack relies on tricking an administrator into running a malicious template.
Mitigation strategies primarily involve upgrading to version 0.3.25 of Backstage, where this issue has been resolved through enhanced input validation routines. In addition to patching, organizations should implement strict least-privilege principles for accounts that have the ability to create or modify scaffolder templates and Confluence content. It is also advisable to review existing templates to ensure they do not rely on untrusted external inputs without additional sanitization layers. Security teams should monitor logs for unusual file system write operations originating from the scaffolder backend service, as these may indicate attempted exploitation of this vulnerability before patches are applied. Regular audits of third-party plugins and modules integrated into the developer portal ecosystem remain essential to maintaining a secure development environment.