Java: Add HTML escapes as XSS sanitizers

Co-Authored-By: Anders Schack-Mulligen <aschackmull@users.noreply.github.com>

Author: Sauyon Lee

java/ql/src/semmle/code/java/security/XSS.qll

@@ -94,6 +94,9 @@ private class DefaultXssSink extends XssSink {
 private class DefaultXSSSanitizer extends XssSanitizer {
   DefaultXSSSanitizer() {
     this.getType() instanceof NumericType or this.getType() instanceof BooleanType
+    or
+    // Match `org.springframework.web.util.HtmlUtils.htmlEscape` and possibly other methods like it.
+    this.asExpr().(MethodAccess).getMethod().getName().regexpMatch("(?i)html_?escape.*")
   }
 }