NSO, an Israeli firm accused of supplying tools for spying on human-rights activists and journalists now faces claims that its technology can use a security hole in WhatsApp, the messaging app used by 1.5 billion people, to break into the digital communications of iPhone and Android phone users.

The products of the NSO Group, which operated in secret for years, were found in 2016 as part of a spying campaign on the iPhone of a now-jailed human-rights activist in the United Arab Emirates through undisclosed Apple security vulnerabilities. Since then, the NSO Group’s spyware has been found on the iPhones of journalists, dissidents, and even nutritionists.

The NSO Group said in a statement on Monday that its spyware was strictly licensed to government agencies and that it would investigate any “credible allegations of misuse.” The company said it would not be involved in identifying a target for its technology, including the lawyer at the center of the latest accusations.

Human Rights organizations have raised concern against the repeatedly evidenced digital attacks targeting human rights defenders, journalists, activists intended to surveil, harass and otherwise interfere with their work.