Google Photos Bug Let Criminals Query Friends, Location

A now-patched vulnerability in the Web version of Google Photos could let cybercriminals learn the details of a user's photo history, Imperva reports.

Through browser-based timing attacks, hackers could analyze image data to learn when a person visited a particular place. It's not a common threat, and it's most effective in a targeted scenario, but it was possible for someone to use a malicious website to access photo data.

Google Photos knows a lot about the people who use it. The service automatically tags each image using metadata (date, location coordinates), and its artificial intelligence engine can detect objects and events that would indicate a wedding, waterfall, sunset, or range of other locations, explains Imperva researcher Ron Masas. Facial recognition tags people also present in the photos.

Coupled with Google Photos' powerful search engine, this detailed information could share a lot about when, where, and with whom a person has been. All of this data can be used in search queries to unearth certain photos – for example: "Photos of me and Ashley from Paris 2018."

Masas decided to investigate Google Photos for side-channel attacks when he learned the extent of its search capabilities. He found the service's search endpoint is vulnerable to an attack called Cross-Site Search, or XS-Search. In a proof of concept, he used the HTML link tag to create multiple cross-origin requests to the Photos search endpoint. Using JavaScript, he measured the time it took for the onload event to trigger. This is the baseline time, or the time it took to query Google Photos' server and receive zero photo results as a response.

With this baseline time, Masas queried "photos of me from Iceland" and compared the two times. If this search took longer, he could infer the user had visited Iceland based on the data. If he added a date, he could know whether photos were taken in a specific time frame. For every place queried, a time longer than the baseline time indicates the user took photos there.

Here's how this vulnerability works: An attacker would have to first send the target a malicious link while that person is logged into Google Photos, by embedding malicious JavaScript inside a Web advertisement or sending a direct message via email or a online messaging service. Malicious JavaScript code creates requests to the Google Photos search endpoint and extracts answers.

"The vulnerability is basically allowing different sites to search for you," Masas explains. As the malicious page is open, an attacker could repeatedly query Google Photos in the background. "By using the advanced search feature, I can ask a lot of questions about you," he adds.

However, once the victim closes the malicious page, the searches stop. "The moment you close the site, I no longer can do that," Masas says. "But I can trick you into opening another site in the future and can continue from there. It does require you to open a website each time."

In his opinion, this isn't a very complex attack but it does have the most value if a hacker is specifically targeting one individual. For example, someone could have used this to determine the location of a high-profile person or know who they have been spending time with. This type of attack "is very hard to detect if you're not looking for it actively," Masas adds. Could a similar vulnerability exist in other online services and applications? "Definitely," he notes. Many developers aren't aware of this problem, and it's important large and small sites learn of it.

This isn't the first time Masas has exposed an attack of this nature. Earlier this month, Facebook patched a flaw he had discovered in the Web version of Facebook Messenger, which could have let attackers view the people with whom someone had been chatting. Similarly, a victim would have to be tricked into opening a bad link; he'd also have to click somewhere on the page. When a new tab opened, the attacker could use the previous page to load the messenger chat endpoint and view which specific person or bots the target had been talking to.

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