Arba Kosos

” Opposition to the Minhag
Given the implication that this minhag not only encouraged stealing but actually rewarded children for doing so, there were many who opposed it, including the Chazon Ish,[11] the Steipler,[12] Rav Shlomo Zalman Auerbach,[13] the Lubavitcher Rebbe[14] and Rav Tzvi Shlezinger.[15] Rav Shemtob Gaguine writes that Sefardim do not have the custom of stealing the afikoman, and he explains that this is because it is forbidden to steal even as a joke since it encourages stealing.[16] And Rav Yosef Kapach writes that this was not the minhag in Teiman as it is forbidden to steal, even for a mitzvah.[17]” via The Seforim Blog