The trio estimated that 99% of Android users were affected because of the slow and fragmented updating that carriers conduct.
Koenings, Nickels and Schaub also outlined more devious damage that a cyber criminal could do. "An adversary could perform subtle changes without the user noticing," they said. "For example, an adversary could change the stored email address of the victim's boss or business partners hoping to receive sensitive or confidential material pertaining to their business."
Google declined to specify how it's addressing the problem, but the German researchers had posed several ways the search giant could plug the security hole.
Among them, Google could modify its services to "reject ClientLogin-based requests from insecure HTTP connections to enforce use of HTTPS," said the researchers, referring to the encrypted data transmission used by online retailers. "HTTPS is already required for the Google Docs API und will be required for Google Spreadsheet and Google Sites APIs in September 2011. It should be mandatory for all of Google's data APIs."
Lookout's Mahaffey suspects that that is exactly the route Google is taking.
"I haven't seen exactly what they're doing," said Mahaffey, "so I can't speculate much, but one solution would be to make it so that authentication tokens aren't sent in the clear anymore."
Paquette assumed the same.
"My guess is that the ClientLogin Protocol had an option that allowed clear text over HTTP, and that Google disabled that on its end by having it say, 'Our end is always going to say "No" to that.' When that happens, the client will decide to send the authentication request encrypted."
While Google could have applied the same fix to the client side -- to each Android phone running an older version of the operating system -- the faster solution was to do it on the server side, Paquette said.
"It's possible that the newest [version of] Android doesn't even offer that [clear text] option," speculated Paquette when asked why only older editions of Android were affected.
HTTPS has been in the news several times this year, as major Web-based services have added it as an option or made it a requirement in an attempt to prevent password theft at unsecured Wi-Fi hotspots.
Last March, for example, Twitter added HTTPS as an option to its users.
Some of those moves were in reaction to last year's release of the "Firesheep" add-on for Mozilla's Firefox that let "pretty much anyone" scan a Wi-Fi network and hijack others' credentials for Amazon, Facebook, Google, Twitter, and other services.
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