[squid-users] Strange user name in SQUID log

Hi!

My SQUID version is 3.1.19. Recently I noticed very strange log record
(strange user name):

1335604655.033 49 192.168.1.20 TCP_DENIED/407 481 HEAD
http://s7.addthis.com/static/r07/sh084.html
%ef%bf%af%ef%be%bf%ef%be%90%ef%bf%af%ef%be%be%ef%be%90%ef%bf%af%ef%be%bf%ef%be%90%ef%bf%af%ef%be%be%ef%be%b1%ef%bf%af%ef%be%bf%ef%be%91%ef%bf%af%ef%be%be%ef%be%80%ef%bf%af%ef%be%bf%ef%be%90%ef%bf%af%ef%be%be%ef%be%b0%ef%bf%af%ef%be%bf%ef%be%90%ef%bf%af%ef%be%be%ef%be%ba%ef%bf%af%ef%be%bf%ef%be%90%ef%bf%af%ef%be%be%ef%be%be%ef%bf%af%ef%be%bf%ef%be%90%ef%bf%af%ef%be%be%ef%be%b4%ef%bf%af%ef%be%bf%ef%be%90%ef%bf%af%ef%be%be%ef%be%b0%ef%bf%af%ef%be%bf%ef%be%90%ef%bf%af%ef%be%be%ef%be%b2%ef%bf%af%ef%be%bf%ef%be%91%ef%bf%af%ef%be%be%ef%be%80%ef%bf%af%ef%be%bf%ef%be%90%ef%bf%af%ef%be%be%ef%be%b0
NONE/- text/html

All my users have their accounts in plain ASCII.
It would not be a big problem (such record occurred only once), but SARG
was unable to process this record and does not generate a report.
I wonder, is it a correct log record, or it's a bug?

-- 
Best regards,
Pavel