As of r36306 [1], the behavior of action=edit's md5 parameter in conjunction with the appendtext and prependtext parameters has changed. Instead of requiring the MD5 hash of the entire article text (which makes appendtext and prependtext kind of useless), the md5 parameter now requires the hash of the concatenation of the prependtext and the appendtext parameter. For example, if you set prependtext=Foo&appendtext=bar , you'll need to set the md5 parameter to the result of md5('Foobar') .

Roan Kattouw (Catrope)

[1] http://svn.wikimedia.org/viewvc/mediawiki?view=rev&revision=36306