Even fairly recent mid-range releases like the Samsung Galaxy A5 are notable by their absence. Related: Samsung Galaxy S6 vs S6 Edge: What's different? Samsung also notes that the update rollout "may vary depending on regions and carriers," so there's no guarantee that even the aforementioned flagship phones will received timely security updates in all markets. Last month, HTC refused to provide its own guarantees, labelling such monthly update promises as "unrealistic." Next, take a look at our smartphone buyers guide video: