May 10th, 2018 applicant. GC Key status changed to the same as yours (taking longer than usual), on May 10th, 2019. We got in touch with Canadian MP and sent a webform to visa office (HK). Both confirmed PA is in security screening by 3 parties. Time frame is unknown and they will contact us when they need some thing or a decision has been made. My husband is from Syria and completed his military service. We met and married in Jordan and now live in China. Not surprised about security screening, but they really should provide applicants with more info than 'we don't have a time frame for you'. Horrific for mental health.
I've read on other posts that secruity screening can take anywhere from 8-18 months, nothing confirmed by official sources though.
Very frustrating position this puts us in, but it's all part of the game. Hope you get processed quickly!