We're sorry to hear about this. If this was a device you really don't trust, you should change your Firefox Account password, and change any passwords saved in Firefox.
Hau entzuteak triste egiten gaitu. Hau fidagarrian ez den gailu bat bada, zure Firefox kontuko pasahitza eta Firefoxen gordeak zeneukan pasahitz guztiak aldatu beharko zenituzke.