Documentation Core Tools Text Unicode Converter

Security Considerations

Understanding security implications when working with Unicode text conversion and processing.

Input Validation

Unicode Range Validation

Valid Range: 0 ≤ code ≤ 0x10FFFF
Invalid Codes: Reject or sanitize codes outside valid range
Surrogate Pairs: Validate proper high/low surrogate pairing

Format Validation

Decimal Input: Ensure numeric values are within valid range
Hexadecimal Input: Validate hex format and range
Escape Sequences: Check for properly formed escape sequences
HTML Entities: Validate entity syntax and numeric values

Character Encoding Security

Homograph Attacks

Unicode allows different characters that look identical:

Latin 'a' (U+0061) vs Cyrillic 'а' (U+0430)
Latin 'o' (U+006F) vs Greek 'ο' (U+03BF)

Mitigation Strategies:

Use Unicode normalization (NFC/NFD)
Implement character set restrictions
Validate against known character sets

Bidirectional Text

Some Unicode characters can change text direction:

RTL Override: U+202E (Right-to-Left Override)
LTR Override: U+202D (Left-to-Right Override)
Pop Directional Formatting: U+202C

Security Implications:

Can hide malicious content
May bypass text filters
Could confuse users

XSS Prevention

HTML Entity Encoding

When converting Unicode to HTML entities:

<!-- Safe -->
&#x3C;script&#x3E;alert('XSS')&#x3C;/script&#x3E;

<!-- Dangerous if not properly escaped -->
<script>
  alert('XSS');
</script>

JavaScript Escape Sequences

In JavaScript contexts:

// Safe
var text = "\u003Cscript\u003Ealert('XSS')\u003C/script\u003E";

// Dangerous if evaluated
var text = "<script>alert('XSS')</script>";

Data Sanitization

Input Sanitization

Remove Control Characters: Filter out dangerous control characters
Normalize Unicode: Use Unicode normalization forms
Validate Encoding: Ensure proper UTF-8 encoding
Length Limits: Implement reasonable length restrictions

Output Sanitization

Context-Aware Escaping: Escape based on output context
Format Validation: Ensure output format is valid
Character Filtering: Remove or replace dangerous characters

Privacy Considerations

Data Storage

Local Storage: Conversion history stored locally in browser
No Server Transmission: Data doesn't leave the user's device
Automatic Cleanup: History automatically limited to 50 entries

Data Handling

Memory Management: Large inputs processed efficiently
Temporary Storage: Data cleared when browser session ends
No Logging: No conversion data is logged or transmitted

Best Practices

Input Handling

// Validate Unicode code point
function isValidUnicode(code) {
  return code >= 0 && code <= 0x10ffff && !(code >= 0xd800 && code <= 0xdfff); // No surrogates
}

// Sanitize input
function sanitizeInput(input) {
  return input.replace(/[\x00-\x08\x0B\x0C\x0E-\x1F\x7F]/g, '');
}

Output Handling

// Safe HTML entity encoding
function encodeHTML(text) {
  return text.replace(/[&<>"']/g, function (match) {
    return '&#' + match.charCodeAt(0) + ';';
  });
}

// Safe JavaScript escaping
function escapeJS(text) {
  return text
    .replace(/\\/g, '\\\\')
    .replace(/'/g, "\\'")
    .replace(/"/g, '\\"')
    .replace(/\n/g, '\\n')
    .replace(/\r/g, '\\r');
}