Wikipedia:High-risk templates

Guideline
This guideline is an extension of the Protection policy.

Page protection should be permanently applied to all templates which have been identified by the community as being of high risk to Wikipedia. These templates should be edited only by administrators and only after a consensus to change the template has been established on the template's talk page.

Templates that are protected per this guideline are listed at List of indefinitely protected pages.

Rationale
Template transclusion has a range of costs and benefits. One cost is that whenever a template is edited, that not only updates the template, but every page that transcludes the template. This means that the squid and parser cached versions of that page are invalidated, and each of the pages must be regenerated by the parser when they are next viewed. This involves significantly more resources than displaying the page from the cache. For example, if template A is transcluded in 100 articles, then editing A effectively changes all 100 articles (plus the template). A high-use template should be edited only if there is a clear need.

This presents a significant problem when templates are the subject of vandalism or reckless editing. Vandalism of high-risk templates can result in significant increases in the load on the servers. It is possible that such vandalism could constitute a denial-of-service attack. Protecting these templates, and allowing them to be edited by admins only after there is a consensus to change the template, reduces or eliminates this risk.

The protection policy already protects high visibility pages (such as the Main Page) and certain "system administration" pages. Some templates are already protected, albeit temporarily, when they are the subject of vandalism, and some are protected for visibility reasons. This guideline advises that permanent protection extend to all templates which pose a high-risk to Wikipedia. This includes a selection of high-volume templates and logical templates identified by the community.

Experience

 * ref and note, which are used in more than 8,000 articles each, were replaced with images of penises several times. Every instance of vandalism on these two templates was reverted within one minute.
 * ed, the most highly-used meta-template (as of 5 November 2005), was replaced with images of penises several times in September 2005. The longest of these instances survived for three minutes; most were reverted within one.

Relevant discussions

 * Wikipedia talk:Protection policy
 * Administrators' noticeboard/IncidentArchive57

Which templates are high-risk?
The proposal does not necessarily propose to apply protection automatically to a list of templates. The process by which high-risk templates are identified may be by individual consensus, by a set of criteria to be implemented by administrators, or by request of Wikimedia developers. However, several tables are provided at List of templates by usage in order to assist the community in determining which templates are high-risk.