Google has fired a security engineer who updated a company tool to notify co-workers of their right to organize, spurring a labor complaint and adding to recent scrutiny of how the company has handled unionization efforts.

Kathryn Spiers, who worked as a security engineer, updated an internal Chrome browser extension so that each time Google employees visited the website of IRI Consultants — the Troy, Michigan, firm that Google hired this year amid a groundswell of labor activism at the company — they would see a pop-up message that read: “Googlers have the right to participate in protected concerted activities.”

Spiers was placed on administrative leave the week of Thanksgiving, the same week the company fired four other employees who claim Google has been engaged in illegal efforts to discourage workers engaged in organizing employees. She was fired Friday.

“We dismissed an employee who abused privileged access to modify an internal security tool,” a Google spokeswoman said in a statement, adding that it was “a serious violation.”

Spiers said she was acting in the interest of her co-workers.

“I was doing nothing more than notifying my co-workers about Google's obligations under labor law,” Spiers said in a text message. “Googlers are expected to take initiative and it's really important we hold upper management accountable."

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The firing comes at a time of heightened tensions at Google as the company has been forced to reckon with employees’ discontent. Earlier this month, the National Labor Relations Board, or NLRB, opened an incestigation into Google's firing of the four workers last month and whether Google discouraged employees from organizing.

Google workers have also organized internal petitions criticizing the company’s plans to build a censored search engine in China, as well as its cloud contract with the Department of Defense to build artificial intelligence for drones. Last year, Google employees organized a walkout across more than 40 offices to protest how they say the company has mishandled allegations of sexual assault and harassment within the company.

Spiers' pop-up message was inserted into a tool that notifies employees of privacy and security concerns about using non-Google tools and services, like warning employees not to upload proprietary information to Dropbox, Spiers said. The tool is managed by the platform security team, for which Spiers worked for almost two years as a security engineer.