HTC has posted a teaser for what is believed to be the One M10. The tweet doesn't reveal much about the phone, but it does contain the hashtag #powerof10. Looking at the image, you can see the outline of a phone with chamfered edges, which based upon what we have already seen would lead us to believe this is the back of the phone.
It's not known whether HTC will continue to tease the One M10 with the #powerof10 hashtag, or if this is a one-off kind of thing. Be sure to keep your eyes out for more details as they are made available.
Source: HTC (Twitter)