September 29, 2023


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Chrome extension Screencastify fixes webcam spy bug • The Register


Screencastify, a preferred Chrome extension for capturing and sharing films from web-sites, was a short while ago found to be vulnerable to a cross-internet site scripting (XSS) flaw that permitted arbitrary internet sites to dupe persons into unknowingly activating their webcams.

A miscreant having advantage of this flaw could then obtain the resulting online video from the victim’s Google Travel account.

Software developer Wladimir Palant, co-founder of advertisement amelioration biz Eyeo, printed a blog article about his conclusions on Monday. He reported he reported the XSS bug in February, and Screencastify’s developers preset it within a working day.

But Palant contends the browser extension carries on to pose a hazard because the code trusts multiple spouse subdomains, and an XSS flaw on any a person of individuals web-sites could probably be misused to assault Screencastify buyers.

The Screencastify web page on the Chrome Internet Retail store states that the browser extension has extra than 10 million people, which is the most price mentioned by store metrics. As Palant factors out, the extension is aimed at the education market, boosting some uncomfortable opportunities.

“The extension grants enough privileges to file a video by means of user’s webcam and get the result,” he points out in his publish. “No person interaction is required, and there are only minimal visible indicators of what’s heading on. It’s even achievable to include your tracks: eliminate the video from Google Drive and use a different concept to close the extension tab opened following the recording.”

What is actually regarding about this is that the extension code offers many other domains these exact same privileges: not just Screencastify, by way of the area, but also Webflow, Teachable, Atlassian, Netlify, Marketo, ZenDesk, and Pendo, just about every through Screencastify subdomains.

And, Palant suggests, neither the Screencastify domain or the subdomains delegated to associates have meaningful Articles Security Plan defense – a way to mitigate XSS hazards.

Palant’s proof-of-thought exploit associated finding an XSS bug inside the Screencastify code, which was not a particularly complicated undertaking because they are really widespread. The NIST database lists pretty much 20,000 of them from 2001 to the present. In accordance to OWASP, “XSS is the next most prevalent situation in the OWASP Prime 10, and is discovered in around two thirds of all programs.”

Palant observed an XSS bug on an mistake web site that will get introduced when a person attempts to submit a video just after previously publishing 1 for an assignment. The web site contained a “View on Classroom” button that sent the user to Google Classroom making use of this code: up(this.courseworkLink)

“It is a query string parameter,” Palant explains in his write-up. “Is there some hyperlink validation in involving? Nope. So, if the query string parameter is a thing like javascript:alert(doc.domain), will clicking this button operate JavaScript code in the context of the domain? It sure will!”

To make that materialize, the attacker would however need to have to trick the target into clicking on this button. But as Palant noticed, the webpage contained no security towards framing, that means it was susceptible to clickjacking. So his proof-of-thought attack did just that, loading the susceptible web site in an invisible body and positioning it less than the mouse cursor so any click on would be passed as a result of to the concealed button.

Thereafter, the webpage could information Screencastify to fetch the victim’s Google entry token and check with Google for the user’s id. It could also record Google Push contents or start off a recording session.

Palant mentioned he described the problem on February 14, 2022, and his message was acknowledged the exact same day. A day later, the XSS on the error page was fastened. The message he obtained also mentioned a long-phrase approach to put into practice Material Safety Plan protection, but as of May possibly 23, in accordance to Palant, that hasn’t transpired on nor, aside from the addition of framing protection.

The API, he noticed, does not seem to have been limited and will however develop a Google OAuth token that can be employed to access a victim’s Google Generate, Palant reported. So far too is the onConnectExternal handler that allows web sites begin video clip recordings.

The Sign-up requested Google irrespective of whether it would care to remark on Palant’s observation that Google Drive accessibility is way too broadly scoped, but we have not heard again.

“So, the concern regardless of whether to continue to keep applying Screencastify at this issue boils down to irrespective of whether you trust Screencastify, Pendo, Webflow, Teachable, Atlassian, Netlify, Marketo and ZenDesk with entry to your webcam and your Google Generate information,” he concludes. “And whether you trust all of these functions to maintain their internet houses cost-free of XSS vulnerabilities. If not, you should uninstall Screencastify ASAP.”

Screencastify did not promptly answer to a get in touch with and email messages trying to get comment. ®


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