TestLink through 1.9.20 allows type juggling for authentication bypass because === is not used.

Multiple SQL injection vulnerabilities in TestLink through 1.9.19 allows remote authenticated users to execute arbitrary SQL commands via the (1) tproject_id parameter to keywordsView.php; the (2) req_spec_id parameter to reqSpecCompareRevisions.php; the (3) requirement_id parameter to reqCompareVersions.php; the (4) build_id parameter to planUpdateTC.php; the (5) tplan_id parameter to newest_tcversions.php; the (6) tplan_id parameter to tcCreatedPerUserGUI.php; the (7) tcase_id parameter to tcAssign2Tplan.php; or the (8) testcase_id parameter to tcCompareVersions.php. Authentication is often easy to achieve: a guest account, that can execute this attack, can be created by anyone in the default configuration.

TestLink before 1.9.20 allows XSS via non-lowercase javascript: in the index.php reqURI parameter. NOTE: this issue exists because of an incomplete fix for CVE-2019-19491.

TestLink through 1.9.16 allows remote attackers to read arbitrary attachments via a modified ID field to /lib/attachments/attachmentdownload.php.