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.
Niqamäy niqak'axaj re re'. We kan man akuqub'an ta chik ak'u'x chi rij ri okisaxel, k'atzinel najäl ri ewan atzij pa ri ataqoya'l richin Firefox, chuqa' ke'ajala' ri ewan taq tzij eyakon pa Firefox.