I see one Linux, one not even Opera, then the rest are Mini. You have any relative URLs in your code?

Opera seems to be the primary culprit. Safe to say we have numerous relative URLs on our pages. Why would that be an issue?

I'm seeing a series of recursive /undefined URLs from Opera in my weblog. It seems they build up indefinitely until the URL becomes too long for php-fpm to grok. It's with numerous versions of Opera as you can see here (is UCBrowser a repackaged Opera?)

Opera/9.80 (MAUI Runtime; Opera Mini/6.1.27412/37.7936; U; en) Presto/2.12.423 Version/12.16
UCWEB/2.0 (Java; U; MIDP-2.0; Nokia203/20.37) U2/1.0.0 UCBrowser/8.7.0.218 U2/1.0.0 Mobile
Opera/9.80 (Android; Opera Mini/14.0.2065/37.7936; U; id) Presto/2.12.423 Version/12.16
Opera/9.80 (J2ME/MIDP; Opera Mini/4.2.17605/37.7936; U; ru) Presto/2.12.423 Version/12.16
SAMSUNG-GT-C3312R Opera/9.80 (J2ME/MIDP; Opera Mini/7.1.33680/37.7936; U; en) Presto/2.12.423 Version/12.16

Presto version looks consistent. Perhaps a known bug?
Access log snippets below (IP addresses removed to protect the innocent). Any thoughts what might be going on here?

thx
mp

www.popsugar.com - - [15/Mar/2016:03:36:03 -0700] 0.001 "GET /static/ck.php?nids[]=32513607&r=601341 HTTP/1.1" 204 0 "http://www.popsugar.com/smart-living/undefined/smart-living/undefined/smart-living/undefined/smart-living/undefined/smart-living/undefined/smart-living/undefined/smart-living/undefined/smart-living/undefined/smart-living/undefined/smart-living/undefined/smart-living/undefined/smart-living/undefined/smart-living/undefined/smart-living/undefined/smart-living/undefined/smart-living/Best-DIY-Gifts-32414022?slide=2" "Opera/9.80 (Android; Opera Mini/7.6.40234/37.7936; U; en) Presto/2.12.423 Version/12.16"

www.popsugar.com - - [15/Mar/2016:03:38:05 -0700] 0.001 "GET /static/ck.php?nids[]=7501917&r=771800 HTTP/1.1" 204 0 "http://www.popsugar.com/fitness/undefined/fitness/undefined/fitness/undefined/fitness/Push-Ups-Variations-Benefits-7501338?slide=0" "Opera/9.80 (Android; Opera Mini/12.0.1987/37.7936; U; en) Presto/2.12.423 Version/12.16"

www.popsugar.com - - [15/Mar/2016:03:24:02 -0700] 0.001 "GET /static/ck.php?nids[]=24324354&r=321460 HTTP/1.1" 204 0 "http://www.popsugar.com/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/undefined/celebrity/Sexiest-Charlize-Theron-Pictures-24324143?slide=3" "Opera/9.80 (J2ME/MIDP; Opera Mini/4.5.40380/37.7936; U; en) Presto/2.12.423 Version/12.16"

Opera/9.80 (X11; Linux zvav; U; en) Presto/2.12.423 Version/12.16
Opera/9.80 (Android; Opera Mini/15.0.2125/37.7936; U; en) Presto/2.12.423 Version/12.16
Opera/9.80 (Android; Opera Mini/7.5.34817/37.7936; U; en) Presto/2.12.423 Version/12.16
Opera/9.80 (Android; Opera Mini/15.0.2125/37.7936; U; en) Presto/2.12.423 Version/12.16
Opera/9.80 (Android; Opera Mini/7.5.33361/37.7936; U; en) Presto/2.12.423 Version/12.16
Opera/9.80 (Android; Opera Mini/7.5.34817/37.7936; U; en) Presto/2.12.423 Version/12.16
Opera/9.80 (Android; Opera Mini/7.5.35721/37.7936; U; en) Presto/2.12.423 Version/12.16
Opera/9.80 (J2ME/MIDP; Opera Mini/4.2.17605/37.7936; U; ru) Presto/2.12.423 Version/12.16
Opera/9.80 (Android; Opera Mini/7.5.35721/37.7936; U; en) Presto/2.12.423 Version/12.16
Opera/9.80 (J2ME/MIDP; Opera Mini/8.0.35676/37.7936; U; en) Presto/2.12.423 Version/12.16
UCWEB/2.0 (Java; U; MIDP-2.0; Nokia203/20.37) U2/1.0.0 UCBrowser/8.7.0.218 U2/1.0.0 Mobile