Denial of service via unbounded token regex backtracking

Regular expression denial of service in NLTK before 3.10.0 allows attackers to saturate a Python process via crafted token searches. Text.findall() delegates to TokenSearcher.findall(), which rewrites the token query and applies re.findall() across a joined corpus without bounding repeated rescans or backtracking. Reachability requires an application to pass attacker-controlled corpus content or token-search expressions; exploitation pins a worker and interrupts service for that process.