Microweber CMS through 2.0.20 contains a stored cross-site scripting vulnerability in the content tagging system that allows admin-authenticated attackers to inject arbitrary JavaScript by submitting malicious payloads via the tagnames parameter of the GET /api/savecontentadmin endpoint, bypassing three independent sanitization controls including XSS middleware that ignores GET requests, a stripunsafe() function that only matches double-quoted onerror attributes, and a titlecase normalizer that passes HTML decimal entity-encoded payloads through unchanged. Attackers can store malicious scripts that execute without user interaction for every visitor to the public blog page and within the admin post editor, enabling session riding through same-origin fetch requests using the CSRF token embedded in the page.

Microweber CMS through 2.0.20 contains a server-side template injection vulnerability that allows authenticated administrators to achieve arbitrary OS command execution by injecting Twig expressions into mail templates. Attackers can exploit the unsandboxed Twig environment in TwigView::render(), which lacks SandboxExtension or a SecurityPolicy, to inject malicious expressions such as filter('system') into mail template bodies stored unsanitized in the database, causing automatic payload execution on each subsequent application event that triggers a mail dispatch.

Microweber CMS through 2.0.20 contains a path traversal vulnerability in the static file controller that allows unauthenticated remote attackers to read arbitrary files by supplying directory traversal sequences in the path query parameter. Attackers can send a single unauthenticated HTTP GET request exploiting the failure of normalizepath() to strip traversal sequences, disclosing sensitive files such as environment configuration files containing credentials and system files.