feat(java): detect Matcher.replaceAll/appendReplacement with tainted replacement strings (CWE-74) - #111
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…replacement strings (CWE-74)
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New taint rule: an attacker-influenced value (map lookup, environment/system property, or request parameter) flowing into the replacement argument of Matcher.replaceAll() or Matcher.appendReplacement().
Java replacement strings interpret '$' and '' as metacharacters: a '$' followed by a digit or '{' is resolved as a back-reference to a capturing group, so a tainted replacement (e.g. a build parameter or environment value such as '$1') throws an unchecked exception ('No group 1') or silently substitutes the wrong text, enabling denial of service or string-manipulation defects. Reviewers should wrap replacements with Matcher.quoteReplacement().
Positive and negative testcases included under testcases/java/. Validated with semgrep 1.172 (pos fires, neg clean).