CVE-2026-112067 in Accessible Form Captcha Extension
Summary
by MITRE • 10/20/2026
The extension hides the correct answer to each CAPTCHA inside the image data of the CAPTCHA itself. Anyone who can request a CAPTCHA image can read the answer from it and submit it, so automated clients can pass the challenge. This applies to the default configuration, because the audio feature that causes the answer to be embedded is enabled by default. Forms that rely on the CAPTCHA as their only protection against automated submissions are exposed to abuse by bots.
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Analysis
by VulDB Data Team • 10/20/2026
The vulnerability described constitutes a critical failure in the implementation of CAPTCHA mechanisms within web applications or browser extensions, specifically stemming from the improper handling of challenge-response data. The core technical flaw lies in the method used to store and retrieve the correct answer for verification purposes. Instead of maintaining the expected value on the server side or using secure cryptographic hashing that prevents reverse engineering, the system embeds the plaintext solution directly within the image file itself. This approach fundamentally violates the principle of separation between challenge presentation and validation logic. By encoding the answer into the pixel data or metadata of the CAPTCHA image, the security mechanism relies entirely on obscurity rather than actual computational difficulty. Since HTTP requests for images are standard web operations accessible to any client capable of making network calls, an attacker can trivially retrieve these images without needing authentication or complex interaction with the application interface.
From a technical perspective, this flaw represents a classic case of insecure direct object references combined with information exposure through side channels. The vulnerability allows automated clients, such as bots or scripts written in Python using libraries like requests and Pillow, to parse the image data and extract the hidden text string. Once extracted, these values can be submitted back to the server alongside other form fields, effectively bypassing the anti-automation control entirely. This is particularly severe because it applies to the default configuration of the extension or application, meaning that users who do not manually alter settings are immediately exposed. The audio feature mentioned in the description likely utilizes steganographic techniques or embedded text layers within the image format to store this data, which can be decoded using standard image processing tools without specialized knowledge of the specific implementation details.
The operational impact of this vulnerability is significant for any system relying on CAPTCHA as its primary defense against automated abuse. Forms that depend solely on this mechanism are vulnerable to a wide range of attacks including credential stuffing, spam submission, brute-force login attempts, and data scraping. Attackers can automate these processes at scale with minimal resource expenditure since the computational cost of solving the CAPTCHA is effectively zero for them. This undermines the integrity of user-generated content, compromises account security by facilitating unauthorized access, and can lead to financial loss or reputational damage depending on the nature of the application. The ease of exploitation means that even low-skilled threat actors can leverage existing tools to compromise these systems, leading to a high likelihood of successful attacks in real-world scenarios.
To mitigate this vulnerability, developers must immediately remove any logic that embeds answers within client-side assets such as images or JavaScript files. Security controls should be implemented server-side where the challenge generation and validation occur without exposing sensitive data to the end user. Industry standards such as CWE-209 (Information Exposure Through an Error Message) and CWE-359 (Exposure of Private Information to an Unauthorized Actor) highlight the severity of leaking internal state through visible or accessible means. Furthermore, this flaw aligns with MITRE ATT&CK techniques related to automated exploitation, specifically those involving bypassing authentication mechanisms like T1110 (Brute Force). Implementations should utilize robust CAPTCHA services that generate challenges dynamically on the server and verify responses without revealing any part of the solution path to the client. Additionally, employing rate limiting and behavioral analysis can provide secondary layers of defense against automated traffic even if a specific vulnerability is present in one component.