Wikipedia:A headline is not a reliable source

This is an essay. It contains the advice or opinions of one or more Wikipedia contributors. This page is not an encyclopedia article, nor is it one of Wikipedia's policies or guidelines, as it has not been thoroughly vetted by the community. Some essays represent widespread norms; others only represent minority viewpoints.

This page in a nutshell: Do not use a headline to support content. Instead, rely solely on what is in the reliable source itself.

This is now part of WP:RS following an RfC. See Wikipedia:Reliable_sources#Headlines

Ignore headlines when you write an article. Headlines are often written by specialists who are not themselves the researchers and journalists who write the articles, therefore the content is verifiable, but not the headline or any ideas not supported by the article. The headline writer has a job to attract attention, generate click-bait titles to juice the number of readers, and for search-engine optimization. Traditionally this was also done for space constraints which are sometimes less relevant in digital reporting. They employ headlinese, an abbreviated form of news writing style used in headlines.

The use of "slam" in headlines has attracted criticism on the grounds that the word is overused and contributes to media sensationalism. The violent imagery of words like "slam", "blast", "rip", and "bash" has drawn comparison to professional wrestling, where the primary aim is to titillate audiences with a conflict-laden and largely predetermined narrative rather than provide authentic coverage of spontaneous events.