Older PHP frameworks sometimes use square brackets to pass whole arrays as GET parameters. The external URL sytnax of MediaWiki cannot handle such links: for example,
[http://www.danishliterature.info/index.php?id=2092&no_cache=1&tx_lfforfatter_pi2[stage]=1&tx_lfforfatter_pi2[uid]=109&tx_lfforfatter_pi2[lang]=_eng Jørgen-Frantz Jacobsen]
should give
<a href="http://www.danishliterature.info/index.php?id=2092&no_cache=1&tx_lfforfatter_pi2[stage]=1&tx_lfforfatter_pi2[uid]=109&tx_lfforfatter_pi2[lang]=_eng">Jørgen-Frantz Jacobsen</a>
but the actual result is
<a href="http://www.danishliterature.info/index.php?id=2092&no_cache=1&tx_lfforfatter_pi2">[stage</a>=1&tx_lfforfatter_pi2[uid]=109&tx_lfforfatter_pi2[lang]=_eng Jørgen-Frantz Jacobsen]
Automatic URL have the same problem. Replacing [ and ] with %5B and %5D usually helps, but is technically incorrect because these are reserved characters and shouldn't be urlencoded (nor do most browsers urlencode them when you copy the URL from the address bar), and it depends on the whim of the url processor whether the urlencoded version will still point to the same resource.
Version: unspecified
Severity: normal