I've just checked, and
wikipedia.com is still running
Apache/1.3.23 (Unix) PHP/4.0.6 mod_fastcgi/2.2.12, which may well be
vulnerable to the chunked-transfer-encoding bug unless it's been patched.
Beta.wikipedia.com is running Apache/1.3.26 (Unix) PHP/4.2.1, so it's
not vulnerable to this bug.