Capgo Default Channel Ambiguity Leading to Unauthorized Bundle Delivery

Executive Summary

This vulnerability exists in Capgo versions before 12.128.2 and involves the handling of multiple public channels for the same app and platform. Specifically, unnamed /updates requests that do not specify a defaultChannel implicitly resolve to a single hidden 'winner' channel. This allows an authorized app or channel manager to create an ambiguous default update state and silently influence which update bundle unnamed clients receive.

As a result, the integrity and predictability of release routing are broken, meaning that clients may receive unexpected or unintended update bundles.

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Detection Guidance

This vulnerability involves multiple public channels existing simultaneously for the same app and platform in Capgo versions prior to 12.128.2, causing ambiguous default update states.

Detection would involve inspecting the channel configuration and update routing logic to identify if multiple public channels coexist for the same app/platform and if unnamed /updates requests resolve to a hidden single channel.

Since the issue is related to database state and update resolution queries, commands should focus on querying the database or API endpoints managing channels and update requests.

• Query the database for public channels per app/platform to check for duplicates.
• Monitor or log /updates requests without a defaultChannel parameter to see which channel they resolve to.
• Use API calls or database queries to verify if multiple public channels exist simultaneously for the same app and platform.

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Impact Analysis

The vulnerability can impact users by breaking the integrity and predictability of software update delivery. Since an authorized app or channel manager can influence which update bundles unnamed clients receive without their knowledge, this could lead to clients receiving unintended or potentially harmful updates.

This could result in inconsistent application behavior, potential security risks if malicious or incorrect updates are delivered, and a loss of trust in the update mechanism.

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Mitigation Strategies

Immediate mitigation involves preventing multiple public channels from coexisting for the same app and platform and ensuring unnamed /updates requests do not resolve ambiguously.

Recommended steps include:

• Upgrade Capgo to version 12.128.2 or later where the issue is fixed.
• Enforce uniqueness of public channels at the database level to prevent duplicates.
• Normalize public-channel state atomically during creation or update operations.
• Make unnamed update selection explicit or reject ambiguous states to maintain release routing integrity.

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