CVE-2022-22748 in Thunderbird
Summary
by MITRE • 12/22/2022
Malicious websites could have confused Firefox into showing the wrong origin when asking to launch a program and handling an external URL protocol. This vulnerability affects Firefox ESR < 91.5, Firefox < 96, and Thunderbird < 91.5.
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Analysis
by VulDB Data Team • 04/28/2026
This vulnerability represents a critical user interface deception flaw that exploits Firefox's handling of external protocol requests and origin display mechanisms. The issue stems from how the browser renders origin information when prompting users to launch external applications or handle URL protocols, creating potential confusion between legitimate and malicious sources. Attackers could craft malicious websites that manipulate the displayed origin information, making it appear as though a trusted domain is requesting protocol handling when in reality the request originates from an untrusted source. This type of vulnerability falls under CWE-601 URL Redirection to Untrusted Site, which specifically addresses situations where web applications redirect users to potentially malicious sites without proper validation of the destination origin. The flaw particularly affects Firefox ESR versions prior to 91.5 and standard Firefox releases before version 96, as well as Thunderbird versions before 91.5, indicating it impacts a broad range of Mozilla-based products that handle external protocol requests.
The technical implementation of this vulnerability involves the browser's protocol handler interface where user prompts are generated for external application launches. When Firefox encounters an external URL protocol request, it displays a dialog box showing the origin domain to inform users about which site is requesting access. However, the vulnerability allows attackers to manipulate or obscure this displayed information through techniques involving carefully crafted HTML content and JavaScript interactions that can influence how the browser presents origin details in these prompts. This manipulation occurs at the user interface level rather than in core protocol handling, making it particularly challenging to detect and prevent through traditional network-based security measures.
The operational impact of this vulnerability extends beyond simple phishing attempts, as it undermines fundamental user trust in browser security mechanisms. Users may inadvertently grant permissions to malicious applications or protocols when they believe they are interacting with legitimate services, potentially leading to full system compromise through various attack vectors including drive-by downloads, credential harvesting, and remote code execution via vulnerable external applications. This vulnerability aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter: JavaScript, where attackers leverage browser-based scripting to manipulate user interface elements and deceive users into performing unintended actions. The attack surface is particularly concerning given that many users regularly interact with external protocols for legitimate purposes such as opening email clients, file managers, or specialized applications.
Mitigation strategies should focus on immediate patch deployment across all affected versions of Firefox ESR, standard Firefox releases, and Thunderbird installations, as this vulnerability represents a clear security risk that cannot be effectively addressed through user education alone. Organizations should implement automated update policies to ensure rapid deployment of security patches across their browser infrastructure. Additionally, security teams should monitor for potential exploitation attempts through network traffic analysis, looking for unusual protocol handler requests or patterns that might indicate the use of this vulnerability in targeted attacks. Browser hardening measures including disabling unnecessary protocol handlers and implementing strict content security policies can provide additional defense-in-depth layers, though these are secondary to the primary patching requirement. The vulnerability demonstrates the importance of maintaining current browser versions and highlights the critical nature of user interface security in preventing social engineering attacks that exploit trust relationships between users and applications.