Android, Google’s mobile OS, is having something of a stressful week right now.

First, several outlets are reporting a security flaw in a couple of HTC Android handsets, including EVO 3D, EVO 4G, and Thunderbolt. The flaw, according to the site Android Police, reportedly exposes private data like emails, phone numbers, and SMS data. Security researcher Trevor Eckhart discovered the flaw, posting his findings in that cybersecurity journal of note, YouTube.

According to people in the know, the flaw is pretty basic. “It’s like leaving your keys under the mat and expecting nobody who finds them to unlock the door,” says Android Police’s Artem Russakovskii, adding (in a several-hundred-word post) that the flaw had left him “speechless.”

HTC, for its part, has issued a statement saying that it “takes our customers’ security very seriously, and we are working to investigate this claim as quickly as possible. We will provide an update as soon as we’re able to determine the accuracy of the claim and what steps, if any, need to be taken.”

It’s the latest in a series of vulnerabilities hackers (mostly of the white-hatted variety, fortunately) have noted. In May, German researchers turned up what was called a “major” security hole; the security firm Symantec has gone so far as to say that the approach to vetting apps “adopted by Google for Android devices is less rigorous and consequently, less secure” than for Apple iOS.

A second piece of bad news for Andoid comes from a competitor: Windows Phone 7.5 Mango, which was released last week. Critical opinion has come pouring in, and Mango, it seems, is destined to be a minor hit: “likable, refreshing, and easy to use”; “WP7 has caught up with Android and iOS in nearly every way, and in some areas it’s even surpassed the other two in functionality”; “the second-best OS out there, after iOS… more cohesive, reliable, pretty, and fast than Android.” If there were a Rotten Tomatoes page for mobile devices, Mango would be certified fresh indeed, meaning one more serious competitor for Android to worry about.

The third piece of trying news for Android might seem counterintuitive: the splashy launch of Amazon Kindle Fire. But isn’t the Kindle Fire an Android tablet itself? In name only. Though the Kindle Fire is built from an earlier version of Android, it’s an Amazon device through and through. The word “Android” is mentioned only once on its product page. And since Amazon has its own app store, an alternative to Android Market, it might be able to lure Android developers into focusing their attentions on Kindle Fire-specific apps. If the balance of power within the Android ecosystem shifts squarely to a tablet that barely pays lip service to the OS that runs it, it’s hard to see how that strengthens Google’s position. The fact that Amazon chose to create a “forked” version of Android means it is essentially independent from Google’s update cycle. Mashable has gone so far as to say that the Kindle Fire has “hijacked” Android. A more apt metaphor might be that of the baby spider who eats its mother.

All in all, a trying week. Then again, if it’s true, as they say, that bad things come in threes, perhaps the folks behind Android can heave a sigh of relief that the worst is behind them.