Security Experts:

XSS Found in Silently Installed Acrobat Chrome Extension

Google Project Zero researcher Tavis Ormandy discovered that a Chrome extension installed silently by Adobe last week had been affected by a cross-site scripting (XSS) vulnerability. Adobe quickly patched the flaw after learning of its existence.

The updates released by Adobe on January 10 for Acrobat and Reader addressed 29 vulnerabilities. However, some users were displeased that the updates also automatically installed an Adobe Acrobat Chrome extension designed for converting web pages into PDF files.

The Windows-only extension requires permission to access data on the websites visited by the user, manage downloads, and communicate with cooperating native apps. The tool also collects some information from the system, but Adobe claims no personal information is involved and the “anonymous data will not be meaningful to anyone outside of Adobe.”

After analyzing the extension, which has roughly 30 million installs, Ormandy identified a DOM-based XSS vulnerability that allowed privileged JavaScript code execution. The expert classified the security hole as “critical severity.”

“I think CSP [Content Security Policy] might make it impossible to jump straight to script execution, but you can iframe non web_accessible_resources, and easily pivot that to code execution, or change privacy options via options.html, etc,” the Google researcher explained in an advisory.

The issue was reported to Adobe on January 12 and it was patched a few days later. It is not surprising that the vulnerability was fixed quickly considering that many of the flaws found in Adobe products are reported by Google Project Zero researchers or through the Chromium Vulnerability Rewards Program.

This was not the first time Ormandy identified a vulnerability in a Chrome extension. Roughly one year ago, the expert revealed that an extension automatically installed by AVG AntiVirus exposed users’ browsing history and other personal data.

Related Reading: Google Researcher Finds Certificate Flaws in Kaspersky Products

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.