CVE-2019-9807 in Firefox
Summary
by MITRE
When arbitrary text is sent over an FTP connection and a page reload is initiated, it is possible to create a modal alert message with this text as the content. This could potentially be used for social engineering attacks. This vulnerability affects Firefox < 66.
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Analysis
by VulDB Data Team • 09/07/2023
This vulnerability represents a cross-site scripting weakness that exploits the improper handling of user-supplied text in FTP connections within the Firefox browser. The flaw occurs when arbitrary text is transmitted through an FTP protocol connection and subsequently processed during a page reload operation. The vulnerability specifically affects Firefox versions prior to 66, indicating it was present in a significant portion of the browser user base during the affected timeframe. The technical mechanism involves the browser's failure to properly sanitize or escape text content received via FTP connections before rendering it in modal alert dialogs, creating a direct pathway for malicious content injection.
The operational impact of this vulnerability extends beyond simple script execution to encompass social engineering attack vectors. Attackers can craft malicious FTP responses containing crafted text that, when processed by the vulnerable browser, generates modal alert messages displaying arbitrary content to unsuspecting users. This creates opportunities for phishing attempts, credential theft prompts, or misinformation campaigns where the alert messages appear to originate from legitimate sources within the user's browser environment. The vulnerability's exploitation requires minimal prerequisites since it leverages existing FTP functionality and browser page reload mechanisms, making it particularly dangerous in environments where users interact with untrusted FTP servers.
From a cybersecurity perspective, this vulnerability aligns with CWE-79 - Cross-Site Scripting, specifically targeting the client-side execution of malicious content through improper input validation. The ATT&CK framework categorizes this under T1566 - Phishing, as it enables attackers to craft convincing social engineering campaigns that exploit user trust in browser modal dialogs. The vulnerability demonstrates how protocol handling inconsistencies can create unexpected attack surfaces, particularly when different communication channels like FTP interact with browser rendering engines. Security professionals should note that this issue highlights the importance of comprehensive input sanitization across all data sources, regardless of their origin or expected processing context. The remediation approach involves implementing proper content sanitization and escaping mechanisms for all user-supplied text before it reaches browser rendering components, particularly in modal dialog contexts where user interaction is expected.
The broader implications of this vulnerability underscore the complexity of modern browser security models where multiple protocols and data sources must be properly isolated and validated. Organizations should ensure their Firefox deployments are updated to version 66 or later to mitigate this risk, while also implementing network monitoring to detect unusual FTP traffic patterns that might indicate exploitation attempts. This vulnerability serves as a reminder that even seemingly benign protocol interactions can create significant security risks when proper input validation is not implemented across all browser components.