A security company has issued a warning after its software was compromised by malicious hackers.
Piriform told users a booby-trapped version of its CCleaner software had been made available in August and September.
Millions of people use the CCleaner program to remove unwanted junk from Android phones and Windows PCs.
Piriform's owner, Avast, said it had managed to remove the compromised version before any harm had been done.
If the malicious hackers who had managed to subvert the software had not been spotted, they could have remotely taken over the devices of the 2.27 million people who had downloaded version 5.33 of the program, said Paul Yung, from Piriform.
Mr Yung said the company had spotted some "suspicious activity" on 12 September that led it to discover version 5.33 had been "illegally modified" before it had been made available to the public.