Neil, your assertion that Israel is the only plausible forger of 27 Israeli citizens with dual passports is surely correct. Israel is the only common denominator. It had a motive; has the history of assassination and the history of ignoring international laws and sovereignty. Its largely trivial, but it would have been very simple for Israeli immigration to ask for the alternative passports of the genuine passport holders on a whole range of pretexts. To apply for Israeli citizenship for a start would have required the original passport. It does mean they will likely have copies of all Israeli dual citizens who gained their alternative citizenship first. So those countries should look to cancel all those passports and issue new ones (although the countries may not know who they are), without reference to Israel, or preferably sending through Israel.
Mexico: Death toll 27 after truck hits religious procession (AP)
from the article: Latest suspect in Dubai hit shares name with Australian-Israeli