Filter doesn't work anymore after update to 2.18
I had a filter in one of my sources.
It filtered all messages with 'Security:' from a RSS-feed, so they didn't appear in selfoss.
The filter is: /^(?!.*(Security:|string2|string3)).*$/
After update to 2.18 the filter doesn't work anymore and the messages are back again.
Can anybody help me with this problem?