Template:COinS safe/doc

Usage

This template is a notice for templates that may be used in citation templates. By default, it indicates the template is safe for use as shown above.

To indicate a template that should not be used in a citation template:

{{COinS safe|n}}

• |addtext= — additional text shown after the main message

When the template is set to not safe, the page is placed into [[:]].

Issue

Citation templates such as Citation Style 1 and Citation Style 2 generate COinS metadata. If a template is used in a citation template field, then it may inject HTML into the metadata.

Compare the rendered HTML for {{cite book}} with |author= using no template and using {{smallcaps}}.

Markup	Renders as
{{cite book |author=Sam Drucker |title=Title}}	Sam Drucker. Title. ​<cite id="CITEREFSam_Drucker" class="citation book">Sam Drucker. ''Title''.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Title&rft.au=Sam+Drucker&rfr_id=info%3Asid%2Ftest2.wikipedia.org%3ATemplate%3ACOinS+safe%2Fdoc" class="Z3988"></span>'"`UNIQ--templatestyles-00000008-QINU`"'​
{{cite book |author={{smallcaps|Sam Drucker}} |title=Title}}	Sam Drucker. Title. ​<cite id="CITEREFSam_Drucker" class="citation book">'"`UNIQ--templatestyles-0000000F-QINU`"'<span class="smallcaps">Sam Drucker</span>. ''Title''.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Title&rft.au=%7F%27%22%60UNIQ--templatestyles-0000000F-QINU%60%22%27%7F%3Cspan+class%3D%22smallcaps%22%3ESam+Drucker%3C%2Fspan%3E&rfr_id=info%3Asid%2Ftest2.wikipedia.org%3ATemplate%3ACOinS+safe%2Fdoc" class="Z3988"></span> <span class="cs1-visible-error error citation-comment">templatestyles stripmarker in <code class="cs1-code">&#124;author=</code> at position 1 ([[Help:CS1 errors#invisible_char|help]])</span>[[Category:CS1 errors: invisible characters]]'"`UNIQ--templatestyles-00000010-QINU`"'​

The author metadata is in the ​rft.aulast​ field. In this case, it is percent-encoded and is rendered as <span class="smallcaps" style="font-variant:small-caps;">Sam Drucker</span>

Reference management software will interpret the entire span as the author name.