CVE-2026-74966 in Firefox
Summary
by MITRE • 08/18/2026
Information disclosure in the Form Autofill component. This vulnerability was fixed in Firefox 154 and Firefox ESR 153.1.
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Analysis
by VulDB Data Team • 08/18/2026
The identified security issue resides within the Form Autofill component of Mozilla Firefox, representing a classic information disclosure vulnerability where sensitive user data is exposed to unauthorized contexts or entities. The core technical flaw involves an improper handling of stored autofill credentials and personal details during form submission processes. Specifically, when users utilize the browser's automated filling capabilities for web forms containing personally identifiable information such as names, addresses, phone numbers, or payment details, a logic error allows this data to be inadvertently exposed beyond its intended scope. This exposure typically occurs through unintended access vectors where scripts from third-party websites or malicious extensions can intercept or read autofill values that should remain isolated within the browser's secure storage mechanisms. The vulnerability stems from insufficient validation of the origin context when retrieving and populating form fields, leading to a breach in data isolation principles that are critical for maintaining user privacy and preventing credential harvesting attacks.
From an operational perspective, this flaw poses significant risks to end-users by facilitating potential identity theft and financial fraud. Attackers leveraging cross-site scripting or malicious ad networks could exploit the exposed autofill data to harvest sensitive information without explicit user interaction beyond visiting a compromised webpage. This undermines the trust users place in browser-based automation features designed for convenience. The impact is particularly severe given that autofill often contains high-value targets such as shipping addresses and financial account details, which are prime assets for cybercriminals engaged in social engineering or direct theft campaigns. By accessing this data, adversaries can construct detailed profiles of victims to facilitate targeted phishing attacks or directly compromise accounts associated with the leaked information.
In terms of industry standard classifications, this vulnerability aligns closely with CWE-200: Information Exposure and CWE-359: Exposure of Private Personal Information to an Unauthorized Actor. These categories highlight the failure in access control mechanisms that should restrict data visibility based on user consent and context. Furthermore, within the MITRE ATT&CK framework, this behavior corresponds to techniques associated with Data from Local System or Browser Credential Dumping, specifically under tactics like Collection and Exfiltration. The vulnerability represents a gap in the browser's ability to enforce strict same-origin policies when interacting with form elements populated by autofill services, allowing malicious scripts to bypass expected security boundaries.
To mitigate this risk, users must ensure they are running Firefox version 154 or later, as well as Firefox ESR 153.1 or newer versions where the patch has been applied. These updates contain code changes that enforce stricter context checks before autofill data is injected into form fields, ensuring that sensitive information is only populated when the originating page meets strict security criteria. Administrators managing enterprise deployments should prioritize updating their fleets to these secure versions immediately to close this exposure window. Additionally, users are advised to review their saved addresses and payment methods regularly through the browser settings, removing any outdated or unnecessary entries to minimize the potential impact of future vulnerabilities. Enabling enhanced tracking protection features can also provide an additional layer of defense by blocking scripts that attempt to interact with form elements in unauthorized ways.