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// String s may be user controllable
// \uFE64 is normalized to < and \uFE64uFE65 is normalized to > using KFKCNFKC
String s = "\uFE64" + "script" + "\uFE65"; 

//validate Validate
Pattern pattern = Pattern.compile("[<>]"); // checkCheck for angle brackets
Matcher matcher = pattern.matcher(s);
if(matcher.find()) {
  System.out.println("found black listed tag");
} else {
  // ... 
}

// normalizeNormalize
s = Normalizer.normalize(s, Form.NFKC);