CVE-2011-0217 in Safari
Summary
by MITRE
Apple Safari before 5.0.6 provides AutoFill information to scripts that execute before HTML form submission, which allows remote attackers to obtain Address Book information via a crafted form, as demonstrated by a form that includes non-visible fields.
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Analysis
by VulDB Data Team • 11/15/2021
This vulnerability exists in Apple Safari web browser versions prior to 5.0.6 and represents a critical information disclosure flaw that undermines the browser's security model for form handling and data protection. The issue stems from the browser's AutoFill functionality which automatically populates form fields with saved user information such as addresses, names, and contact details from the Address Book. When a form is submitted, Safari's AutoFill system was designed to provide this information to scripts that execute before the form submission process begins, creating a window of opportunity for malicious actors to intercept sensitive data.
The technical implementation flaw occurs in the timing and scope of AutoFill data exposure within the browser's JavaScript execution environment. When a crafted HTML form contains non-visible input fields that trigger AutoFill behavior, attackers can leverage this vulnerability to extract Address Book information from unsuspecting users. This exploitation technique specifically targets the period between when a form is loaded and when it is submitted, allowing malicious scripts to access the AutoFill data that would normally be restricted to the form submission context. The vulnerability demonstrates a failure in proper access control and data isolation between browser components and client-side scripts.
The operational impact of this vulnerability is significant as it enables remote attackers to perform unauthorized data extraction from users' Address Book information without their knowledge or consent. Attackers can create malicious websites that contain forms with hidden fields designed to trigger AutoFill behavior, then capture the sensitive information that gets populated into these fields. This creates a persistent threat vector where users' personal contact information, including names, addresses, phone numbers, and email addresses, can be systematically harvested. The attack requires no user interaction beyond visiting a malicious website, making it particularly dangerous for widespread exploitation.
This vulnerability maps directly to CWE-200, which describes "Information Exposure," and aligns with ATT&CK technique T1531 for "Account Access Removal" and T1566 for "Phishing" through the use of malicious web content. The flaw represents a failure in proper input validation and output sanitization within the browser's AutoFill implementation, creating an information disclosure channel that violates the principle of least privilege. Security researchers have noted that this vulnerability demonstrates how seemingly benign browser features can become attack vectors when proper security boundaries are not maintained between different execution contexts. The issue highlights the importance of maintaining strict isolation between user data and client-side script execution environments, particularly in web browsers where multiple security models must coexist.
The recommended mitigations include upgrading to Safari 5.0.6 or later versions where Apple has implemented proper access controls to prevent AutoFill data exposure to pre-submission scripts. Organizations should also implement browser hardening policies that restrict AutoFill functionality where possible and deploy web application firewalls to detect and block malicious form submissions. Users should be educated about the risks of visiting untrusted websites and should regularly update their browsers to ensure they have the latest security patches. Additionally, security monitoring should include detection of unusual form submission patterns that might indicate exploitation attempts targeting this vulnerability.