CVE-2007-1084 in Firefox
Summary
by MITRE
Mozilla Firefox 2.0.0.1 and earlier does not prompt users before saving bookmarklets, which allows remote attackers to bypass the same-domain policy by tricking a user into saving a bookmarklet with a data: scheme, which is executed in the context of the last visited web page.
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Analysis
by VulDB Data Team • 03/07/2025
The vulnerability described in CVE-2007-1084 represents a significant security flaw in Mozilla Firefox versions 2.0.0.1 and earlier that fundamentally undermines the browser's security model. This issue stems from the browser's failure to implement proper user consent mechanisms when processing bookmarklets, which are small JavaScript snippets designed to perform automated tasks within web browsers. The vulnerability specifically targets Firefox's handling of bookmarklets that utilize the data: scheme, a URI scheme that allows embedding of data directly within the URI itself, bypassing normal cross-origin restrictions that typically protect users from malicious code execution.
The technical flaw manifests through a sophisticated social engineering attack vector that exploits the browser's trust model. When users encounter a malicious bookmarklet, Firefox automatically saves it without prompting for user confirmation, effectively removing the security barrier that should prevent unauthorized code execution. The data: scheme bookmarklets can contain JavaScript code that executes in the context of the last visited webpage, meaning that if a user visits a malicious website and then saves a bookmarklet, the code will run with the privileges and context of that original website. This creates an environment where attackers can circumvent the same-domain policy that normally prevents scripts from one domain from accessing resources or executing commands on another domain, thereby undermining fundamental web security principles.
The operational impact of this vulnerability is particularly severe as it enables attackers to perform actions that would normally be restricted by browser security policies. The flaw allows for cross-site scripting attacks where malicious code can be executed within the context of trusted domains, potentially leading to session hijacking, data theft, or privilege escalation. The vulnerability is especially dangerous because it operates silently in the background, with users unknowingly saving malicious bookmarklets that can execute arbitrary code whenever they choose to use them. This creates a persistent threat vector that can remain active long after the initial compromise, making it difficult for users to detect and remediate the security issue.
This vulnerability aligns with CWE-346, which addresses the lack of validation of data source authenticity, and specifically relates to CWE-20, which covers improper input validation. The attack pattern follows techniques described in the ATT&CK framework under T1059.007 for JavaScript execution and T1203 for social engineering. The flaw demonstrates how insufficient user interaction requirements can create security bypass opportunities, as the browser fails to validate or confirm the source of bookmarklet content before saving it. Organizations and users should implement mitigation strategies including immediate browser updates to patched versions, user education about bookmarklet security, and network monitoring for suspicious bookmarklet activity. The vulnerability also highlights the importance of proper privilege separation and the need for explicit user consent mechanisms when dealing with potentially dangerous code execution contexts, particularly those that can execute within the security boundaries of previously visited websites.