Executive Summary

This vulnerability is an HTML injection issue in the Mailgen Node.js package versions prior to 2.0.30. It occurs in the Mailgen.generatePlaintext(email) method when it processes user-generated content without properly sanitizing it. This allows malicious HTML code to be injected into plaintext emails, potentially causing unintended rendering or execution of HTML in email clients. The vulnerability was fixed in version 2.0.30 by improving the HTML tag stripping mechanism. [1, 2]

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Impact Analysis

If you use Mailgen.generatePlaintext(email) with user-generated content in affected versions, an attacker could inject malicious HTML into plaintext emails. This could lead to unexpected email content rendering or potentially exploit email client vulnerabilities. Although the severity is low, it may affect the integrity and safety of transactional emails sent using Mailgen. [1]

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Detection Guidance

To detect this vulnerability, you should check if your project uses the Mailgen package with a version prior to 2.0.30 and if it calls the Mailgen.generatePlaintext(email) method with user-generated content. There are no specific network or system commands provided to detect the vulnerability directly. However, you can inspect your package.json or lock files for the Mailgen version and review your code for usage of generatePlaintext with unsanitized input. [1]

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Mitigation Strategies

Immediate mitigation steps include upgrading the Mailgen package to version 2.0.30 or later, where the vulnerability is patched. As a workaround, manually strip all HTML tags from any user-generated content before passing it to Mailgen.generatePlaintext(email). This can be done by applying a robust HTML tag stripping method that handles multiline tags, similar to the updated regular expression in the patch. This prevents malicious HTML injection in plaintext emails. [1, 2]

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