What potential security risks should be considered when handling PDF attachments in a PHP forum environment?

When handling PDF attachments in a PHP forum environment, potential security risks to consider include the possibility of malicious code being embedded within the PDF file, leading to exploits such as cross-site scripting (XSS) attacks or remote code execution. To mitigate these risks, it is important to validate the file type and content of the PDF attachment before processing or displaying it to users. Additionally, implementing proper file upload restrictions, such as limiting file size and ensuring secure file storage practices, can help prevent potential security vulnerabilities.

// Validate PDF file type before processing
$allowedTypes = ['application/pdf'];
$uploadedFileType = $_FILES['pdf_attachment']['type'];

if (!in_array($uploadedFileType, $allowedTypes)) {
    // Handle invalid file type error
}

// Validate PDF file content before processing
$filePath = $_FILES['pdf_attachment']['tmp_name'];
if (mime_content_type($filePath) !== 'application/pdf') {
    // Handle invalid file content error
}

// Implement file upload restrictions
$maxFileSize = 1048576; // 1MB
if ($_FILES['pdf_attachment']['size'] > $maxFileSize) {
    // Handle file size limit exceeded error
}

// Save the PDF attachment securely
$uploadDirectory = 'uploads/';
$uploadedFileName = $_FILES['pdf_attachment']['name'];
$targetFilePath = $uploadDirectory . $uploadedFileName;

if (move_uploaded_file($_FILES['pdf_attachment']['tmp_name'], $targetFilePath)) {
    // File uploaded successfully
} else {
    // Handle file upload error
}