phpMyFAQ has Potential Authenticated Path Traversal in PDF Export

Summary

There is an authenticated path traversal condition in the PDF export functionality, specifically within the PDF image resolution logic.

The issue may allow a privileged FAQ editor to cause the application to attempt reading files outside the intended content directory during PDF generation.

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Affected Component

File: src/phpMyFAQ/Export/Pdf/Wrapper.php

Function: concatenatePaths()

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Root Cause

The path resolution logic relies on locating the substring "content" within a user-controlled path:

$pos = strpos($trimmedFile, 'content');
$relativePath = substr($trimmedFile, (int) $pos);

If "content" is not present, strpos() returns false, which becomes 0 when cast to an integer.

As a result, the entire attacker-controlled path is preserved.

Example:

$trimmedFile = "../../../etc/passwd";
$pos = false;
$relativePath = "../../../etc/passwd";

The resulting path is later processed by:

file_get_contents($resolvedPath);

without canonicalization or a root-directory containment check.

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Observed Data Flow

FAQ Content
    ->
PDF Export
    ->
WriteHTML()
    ->
Wrapper::Image()
    ->
concatenatePaths()
    ->
file_get_contents()

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Potential Impact

Based on code review, a user with FAQ editing privileges may be able to store HTML containing crafted image paths that are processed during PDF generation.

Potential consequences may include:

• Path traversal outside the intended content directory
• Local file read attempts during PDF export
• Possible disclosure of readable files depending on file type, sanitization behavior, and PDF rendering constraints

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Discovery Method

This issue was initially detected by an internally developed SAST tool during analysis of the phpMyFAQ source code.

The finding was then manually investigated and validated through code review.

While the original scanner output classified the issue as a generic path traversal/local file inclusion pattern, manual analysis identified the specific root cause in the path resolution logic of concatenatePaths().