<ul><li>Fixed CRITICAL: <code>occurance()</code> in functions.php divided by zero when title/description/keywords/headings had 0 words (page with no meta tags, empty headings) — DivisionByZeroError caused HTTP 500 on every analysis; added zero guard (CRITICAL)</li><li>Fixed CRITICAL: <code>index_app.php</code> was a full standalone HTML document with <code>&lt;!DOCTYPE html&gt;</code> wrapper and <code>session_start()</code> — same nested-document bug as keyword_density causing jQuery version conflict; removed wrapper and session_start (CRITICAL)</li><li>Fixed CRITICAL: <code>index_app.php</code> loaded jQuery 1.10.2 from Google CDN after platform jQuery 2.1.4, overwriting it and breaking all UBOLD4 plugins (CRITICAL)</li><li>Fixed HIGH: <code>highlight()</code> passed raw user keyword input directly to <code>preg_replace()</code> regex — special chars in keyword could cause regex error or ReDoS; added <code>preg_quote()</code> (HIGH)</li><li>Fixed HIGH: <code>[metaTags][description][value]</code> and keywords accessed without null check — if page had no meta tags getUrlData returns false; added null coalescing (HIGH)</li><li>Fixed MEDIUM: <code>file_get_contents_curl()</code> called with 3 args at canonical check — function only accepts 1; removed unused args (MEDIUM)</li><li>Fixed MEDIUM: 4 undefined array key warnings on unmatched regex captures ([0], [3], [1], [0]) — added null coalescing and empty() guard (MEDIUM)</li></ul>