> For the complete documentation index, see [llms.txt](https://repo.4pfsec.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://repo.4pfsec.com/portswigger-labs/authentication.md).

# Authentication

Conceptually at least, authentication vulnerabilities are some of the simplest issues to understand. However, they can be among the most critical due to the obvious relationship between authentication and security. As well as potentially allowing attackers direct access to sensitive data and functionality, they also expose additional attack surface for further exploits.

![](/files/R0HGURT0ddljqA69LUhR)

<img src="/files/R0HGURT0ddljqA69LUhR" alt="" data-size="original">