Fix XSS Vulnerability in amp-access based samples (#1198)
Fix XSS Vulnerability in amp-access based samples (#1198)

Entering an URL such as https://ampbyexample.com/samples_templates/comment_section/submit?returnurl=javascript:alert`xss`//%09
allows attackers to run arbitrary code.
ampproject/amp-by-example,ampproject/amp-by-example,ampproject/amp-by-example,ampproject/amp-by-example