What are the security implications of allowing a file to be uploaded to a web server without explicit user selection?

Allowing a file to be uploaded to a web server without explicit user selection can pose security risks such as potential malware uploads or unauthorized access to sensitive files. To mitigate these risks, it is important to always validate and sanitize user input before allowing any file uploads. 

// Validate and sanitize file upload
if(isset($_FILES['file'])) {
    $file_name = $_FILES['file']['name'];
    $file_tmp = $_FILES['file']['tmp_name'];
    
    // Add additional validation and sanitization steps as needed
    
    move_uploaded_file($file_tmp, "uploads/" . $file_name);
    echo "File uploaded successfully";
} else {
    echo "No file selected for upload";
}

Keywords

file upload web server security implications PHP user selection

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