That looks like the icon for Adobe Updater alright. You’ll typically find the program Adobe_Updater.exe in a directory such as Program Files\Common Files\Adobe\Update6\

It’s used to control auto updates of programs such as Acrobat, Reader, Photoshop, etc.

It occasionally needs to be updated itself. See for example:

Adobe Updater 6.2 Update
http://www.adobe.com/support/downloads/detail.jsp?ftpID=4509

If in doubt about the legitimacy of the update prompt, check the version you have installed and then go to the Adobe site - perhaps the forums would be a good place - and see if there’e a later version than what you have.

Perhaps it’s not in avast!'s suggested updates list because it isn’t known to be vulnerable to exploits … my guess.