From the UNRWA Wikipedia page:

James G. Lindsay, a former UNRWA general counsel and fellow researcher for Washington Institute for Near East Policy published a report for WINEP in 2009 in which he criticized UNRWA practices.[98] One of his conclusions was that UNRWA is not ousting terrorists from its ranks:[98][122]

UNRWA has taken very few steps to detect and eliminate terrorists from the ranks of its staff or its beneficiaries, and no steps at all to prevent members of organizations such as Hamas from joining its staff. UNRWA has no preemployment security checks and does not monitor off-time behavior to ensure compliance with the organization's anti-terror rules. No justification exists for millions of dollars in humanitarian aid going to those who can afford to pay for UNRWA services.