SAN FRANCISCO — Vacation rental company HomeAway Inc. and its online payment partner YapStone Inc. didn’t do enough to prevent a yearlong security breach that exposed user information including bank account and Social Security numbers, plaintiffs lawyers allege in suit filed Monday. HomeAway, which operates HomeAway.com, VRBO.com and VacationRentals.com, alerted users in September that its security had been compromised, leaving data accessible to outsiders from July 2014 to August 2015, according to the suit. Plaintiffs claim the breach compromised the names, email addresses, physical addresses, dates of birth, bank account information and Social Security numbers of property owners and managers.