[wp-trac] [WordPress Trac] #64376: redirect_canonical() causes unnecessary 301 redirects for query string encoding variants (+ vs %20)

[WordPress Trac]

#64376: redirect_canonical() causes unnecessary 301 redirects for query string
encoding variants (+ vs %20)
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 Reporter:  robbertvancaem                       |       Owner:  (none)
     Type:  defect (bug)                         |      Status:  new
 Priority:  normal                               |   Milestone:  Future
                                                 |  Release
Component:  Canonical                            |     Version:
 Severity:  normal                               |  Resolution:
 Keywords:  has-patch has-unit-tests needs-      |     Focuses:
  testing                                        |  performance
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Comment (by jbiggs):

 Just wanted to add my 2c here. I struggled with this for the whole of
 Easter weekend until I figured out what was happening. Upon fixing the
 issue I discovered this thread.

 I can see how this could potentially be used to create a denial-of-service
 condition on a site.

 For example, if a host like Kinsta is ignoring UTM parameters for cache
 variation (which it does), and repeated requests are sent just as the
 homepage cache is about to expire using a URL such as
 https://site.com/?utm_content=test:123, it could cause the homepage to
 cache a 301 redirect loop. Once that redirect response is cached, all
 users could be served the loop until the cache expires.

 That is effectively what I was seeing happen to my site, although it
 wasn't malicious, we were just getting that much Google Ads traffic that
 occasionally it was happening by chance.

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Ticket URL: <https://core.trac.wordpress.org/ticket/64376#comment:12>
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