My logs are showing bingbot / msnbot appending %2Findex.php to some of my urls. Any idea why? This makes them invalid and if any users were redirected with it, it would not take them to the correct page. I've poked around a bit and noticed that Findex is a common string in a referrer URL, but it is not valid on my website.
UPDATE
Some Details From the log: These IPs are both listed as owned by Microsoft
157.55.39.21 - - [11/Jan/2016:10:09:02 -0800] "GET /index.php?grade=7&page=chemistry&page2=crystallization%2Findex.php HTTP/1.1" 200 7308 "-" "Mozilla/5.0 (compatible; bingbot/2.0; +http://www.bing.com/bingbot.htm)"
207.46.13.150 - - [11/Jan/2016:10:00:22 -0800] "GET /index.php?grade=1&page=Games%2Findex.php HTTP/1.1" 200 6427 "-" "Mozilla/5.0 (compatible; bingbot/2.0; +http://www.bing.com/bingbot.htm)"
%2Fis an encoded slash and on Apache, an encoded slash in the URL-path part of the URL will typically generate a 404. "redirected with it" - what response is returned for such URLs? – MrWhite Jan 12 '16 at 08:38%2Findex.php, is this URL otherwise valid? How is this URL generated? Where do the values for thepageandpage2URL parameters come from? – MrWhite Jan 13 '16 at 09:43