CVE-2016-1937 in Firefox
Summary
by MITRE
The protocol-handler dialog in Mozilla Firefox before 44.0 allows remote attackers to conduct clickjacking attacks via a crafted web site that triggers a single-click action in a situation where a double-click action was intended.
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Analysis
by VulDB Data Team • 07/06/2022
The vulnerability identified as CVE-2016-1937 represents a significant security flaw in Mozilla Firefox versions prior to 44.0, specifically within the protocol-handler dialog implementation. This vulnerability enables remote attackers to execute sophisticated clickjacking attacks by crafting malicious websites that manipulate user interactions through deceptive dialog prompts. The core issue manifests when users encounter protocol handler dialogs that are designed to handle external protocol requests such as mailto:, tel:, or other URI schemes, creating an environment where user intent can be misdirected through carefully constructed malicious web pages.
The technical flaw exploits the inherent design of Firefox's protocol handler dialog mechanism, where the user interface does not adequately distinguish between single-click and double-click actions that are typically required for different protocol handling operations. Attackers can construct web pages with overlapping transparent layers or carefully positioned elements that cause users to inadvertently trigger single-click actions when they intend to perform double-click operations. This misalignment between user expectation and actual system behavior creates a dangerous operational environment where malicious actors can manipulate protocol handling workflows. The vulnerability specifically affects how Firefox presents and processes protocol handler dialogs, particularly when these dialogs are triggered through web content rather than direct user interaction with the browser's interface.
The operational impact of this vulnerability extends beyond simple user inconvenience to encompass potential security breaches and unauthorized protocol executions. When users encounter malicious websites, they may unknowingly trigger protocol handlers that open external applications, send emails, initiate phone calls, or perform other actions that could compromise system security. The clickjacking aspect means that attackers can effectively hijack user interactions without their knowledge, potentially leading to unauthorized access to sensitive systems or data exfiltration. This vulnerability particularly affects users who frequently interact with web content that triggers protocol handlers, as the attack surface expands with each legitimate use of such functionality.
Security professionals should note that this vulnerability aligns with CWE-428, which addresses the weakness of "Security Misconfiguration" and specifically relates to improper handling of user interaction in web applications. The issue also connects to ATT&CK technique T1059.007, which covers "Command and Scripting Interpreter: Python," as malicious protocol handlers could potentially execute Python scripts or other command-line operations. Organizations should implement immediate mitigations including updating Firefox to version 44.0 or later, where the vulnerability has been patched through enhanced dialog handling and user interaction validation mechanisms. Additional protective measures include implementing content security policies, disabling unnecessary protocol handlers, and conducting user awareness training to recognize potentially malicious web interactions that could exploit this vulnerability.