Interesting, I just got routed to a web page displaying an apple logo stating "Secure Connection Failed - svn.boost.org Uses and Invalid Security Certificate. The Certificate is not trusted..... [yada yada].... CALL TOLL FREE 1-855-169-3948"
There was also a pop-up window that descended below the bottom of my monitor, rendering no access to any buttons that may have been available. The popup window stated "http://mac-protecton.com Critical Security Warning! your System is infected with a malicious adward attack. Please call tech support at 1-855-469-3948and provide error code WBACK7917... [yada yada]... Please call customer service at 1-855-469-3948to [not a typo] resolve issues."
Clearly spam, but how did this page load? I wasn't going to 'svn.boost.org' but instead to ussoccer.com - also, I've recently visited sites pertaining to travel, similar to OP.
To resolve, I quit Safari, and on restart the same page/popup loaded. I quit Safari again but was fast enough to close the window before it loaded. I also had to close multiple 'unknown' tabs before an expected page loaded.
Clearly a scam and didn't call the number. Hopefully this is an isolated incident. Screen grabs of offending pages attached.