Executive Summary

The vulnerability exists in my little forum, a PHP and MySQL based internet forum, prior to version 20260208.1. The application does not properly filter the phar:// protocol in URL validation. This allows attackers to upload a malicious Phar Polyglot file disguised as a JPEG image via the image upload feature. When the forum processes BBCode [img] tags, it triggers Phar deserialization, which can be exploited through Smarty 4.1.0's POP chain to achieve arbitrary file deletion.

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Impact Analysis

This vulnerability can allow an attacker to delete arbitrary files on the server hosting the forum. Since the attacker can upload a malicious file disguised as an image and trigger its deserialization, they can exploit the system to remove files without authorization, potentially leading to data loss, service disruption, or further compromise of the server.

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Compliance Impact

I don't know

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Detection Guidance

I don't know

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Mitigation Strategies

To mitigate this vulnerability, you should update my little forum to version 20260208.1 or later, where the issue with filtering the phar:// protocol in URL validation has been fixed.

Until the update is applied, consider disabling or restricting the image upload feature to prevent attackers from uploading malicious Phar Polyglot files disguised as JPEGs.

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