Broken ColorThemes because of double URL encoding

On xwiki.org we have a page on the main wiki xwiki:XWiki.XWikiOrgSkinExtension that is used in the subwiki's 'Administration - Page Elements' in the 'HTTP Meta Info' section.

The call is:

$xwiki.ssx.use("xwiki:XWiki.XWikiOrgSkinExtension", {'colorTheme': "${xcontext.database}:$!xwiki.getUserPreference('colorTheme')"})

On the 5.2 xwiki.org version this call worked without problems and it was resolved for example in:

http://www.xwiki.org/xwiki/bin/ssx/XWiki/XWikiOrgSkinExtension?language=en&colorTheme=commons%3AColorThemes.CommonsCT

when called from http://commons.xwiki.org/.

Example of CSS used (xwiki:XWiki.XWikiOrgSkinExtension):

#template('colorThemeInit.vm')
#headerglobal, #footerglobal  {
  background-color: $theme.pageHeaderBackgroundColor;
}

was transformed in

#headerglobal,#footerglobal {
 background-color:#243825;
}

After the upgrade to 5.4, the call resolves to

http://www.xwiki.org/xwiki/bin/ssx/XWiki/XWikiOrgSkinExtension?language=en&colorTheme=commons%253AColorThemes.CommonsCT

There is a problem with the encoding.
If until now ':' resolved to '%3A', now '%' is double encoded resulting in '%253A'.

The resourse 'commons%253AColorThemes.CommonsCT' does not exists, thus xwiki:XWiki.XWikiOrgSkinExtension fallsback on the defaults (#fff)

#headerglobal,#footerglobal {
 background-color:#fff;
}