CVE-2025-55030 in Firefox
Summary
by MITRE • 08/20/2025
Firefox for iOS would not respect a Content-Disposition header of type Attachment and would incorrectly display the content inline rather than downloading, potentially allowing for XSS attacks This vulnerability affects Firefox for iOS < 142.
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Analysis
by VulDB Data Team • 10/12/2025
This vulnerability in Firefox for iOS represents a critical breakdown in web security mechanisms that directly impacts how the browser handles file downloads and content rendering. The issue stems from the browser's failure to properly interpret the Content-Disposition HTTP header, specifically when it is set to attachment type. This header is a standard web security feature designed to instruct browsers on how to handle specific content, with attachment indicating that the content should be downloaded rather than displayed inline within the browser window. The flaw creates a significant security gap that could be exploited by malicious actors to bypass intended security controls.
The technical implementation error manifests in the iOS browser's content processing pipeline where it disregards the attachment directive and instead renders the content directly in the browser context. This behavior creates a dangerous scenario where attackers can craft malicious web pages that appear to offer downloads but actually execute content inline, potentially allowing for cross-site scripting attacks to be delivered through what users expect to be safe download operations. The vulnerability specifically affects versions prior to 142, indicating that this was a targeted issue within a particular release cycle that had not yet been addressed by the development team.
From an operational security perspective, this vulnerability exposes users to potential exploitation through malicious websites that could serve content designed to bypass normal security boundaries. When content is displayed inline instead of being downloaded, it places the content execution within the browser's security context where it can interact with the page's JavaScript environment and potentially access sensitive user data or perform actions that would normally be restricted during a proper download operation. This misinterpretation of web standards creates an attack surface that could be leveraged for various malicious activities including credential theft, session hijacking, or delivery of additional malware through script injection.
The impact of this vulnerability aligns with common attack patterns documented in the attack framework, particularly those involving content injection and execution context manipulation. This issue demonstrates a failure in proper HTTP header processing that could be categorized under CWE-116 for improper encoding or handling of escape characters in web applications. Security researchers should note that this vulnerability represents a regression or implementation flaw that could potentially be exploited in conjunction with other attack vectors to create more sophisticated threats. The lack of proper handling of Content-Disposition headers also violates fundamental web security principles outlined in various security standards that emphasize the importance of respecting server-provided content handling instructions.
Organizations and users should immediately update to Firefox for iOS version 142 or later to remediate this vulnerability, as the issue represents a direct threat to user security when browsing untrusted websites. Security teams should also monitor for any related vulnerabilities that might exploit similar header processing issues, and consider implementing additional network-level protections or content filtering measures until full patch coverage is achieved. The vulnerability underscores the importance of proper security testing for mobile browser implementations and highlights the need for robust handling of standard HTTP security mechanisms to prevent such context manipulation attacks from succeeding.