Opposition coalition 1Sambayan said its mobile membership application was hacked over the weekend.
Brother Armin Luistro, one of the coalition's convenors, said the data breach of 1Sama Ako, an application for supporters and volunteers, occurred on June 12.
Due to the breach, 1Sambayan placed the entire system under maintenance mode to prevent further access to their data.
"Sa aming paunang pagsisiyasat, napag-alaman naming ang mga datos ay na-expose sa pamamagitan ng isang Application Programming Interface o API na aming ginamit sa aming huling bersyon ng App," Luistro said in a statement.
"Amin ding natukoy na ang breach ay nanggaling sa isang propesyunal na hacker na may 'di magandang intensyon at itinaon sa isang malaking okasyon na inilunsad ng 1Sambayan," he added.
The group already reported the attack to the National Privacy Commission. It also notified registered volunteers affected by the breach, warned them of potential risks and offered technical support if they needed it.
1Sambayan said the API has been patched and it has already coordinated with an independent audit team to reassess its system security protocols.
The application will remain offline until it gets a green light from its security audit team, the group said.
"Hindi namin papayagan ang anumang pagtatangka na idiskaril ang aming hangarin para sa mas maayos na liderato sa 2022 at pigilan ang pagsusulong ng aming adhikain," 1Sambayan said.
On June 12, the coalition bared six names of its potential candidates for president and vice president for the upcoming 2022 polls.
1Sambayan revealed that among their nominees were Vice President Leni Robredo, former Senator Antonio Trillanes IV, Senator Grace Poe, CIBAC party-list Representative Eduardo Villanueva, lawyer Jose Manuel "Chel" Diokno, and Batangas Representative Vilma Santos-Recto. —Ma. Angelica Garcia/NB, GMA News