Web::Simple versions before 0.037 for Perl do not escape single quotes in HTML::Tags output. HTML::Tags and XML::Tags escape a plain string value by replacing only &, ", < and > with entities. A value interpolated into a single-quoted attribute, as in <a href='$value'>, can therefore close the attribute and add new ones, such as an event handler. Double-quoted attributes are not affected. An attacker who controls a value that an application interpolates into a single-quoted attribute can inject script into the generated page.
https://www.cve.org/CVERecord?id=CVE-2026-5090
https://metacpan.org/release/ETHER/Web-Simple-0.037/changes
https://github.com/p5sagit/Web-Simple/commit/de0b7743f7015ec2c1c678dfdaa4bc6f5ccfb640.patch