Grindr faces the prospect of legal action by hundreds of users who will allege that the dating app shared highly sensitive personal information, including in some cases their HIV status, with advertising companies. The law firm Austen Hays is to file a claim on Monday in London’s high court alleging that the US owner of the app breached British data protection laws. The firm alleges that thousands of UK Grindr users had their information misused. So far 670 people have signed up to the claim, and the firm said “thousands” more people had expressed interest in joining.