Problem about proxy action

Describe the bug

I find a problem about proxy action.
If access a specified webpage file, such as "http://a.com/a/index.html", it can be successfully forwarded.
If access a directory, such as "http://a.com/a/", the error_log can log the url will be forwarded, but actually it cannot be forwarded.

Logs and dumps

[Wed Jun 12 11:04:12.784758 2024] [security2:error] [pid 97647:tid 139691269490432] [client 10.16.18.12:49131] [client 10.16.18.12] ModSecurity: Access denied using proxy to (phase 2) http://www.test1.com/a/index.html. detected XSS using libinjection. [file "/www/server/apache/conf/modsecurity/rules/REQUEST-941-APPLICATION-ATTACK-XSS.conf"] [line "100"] [id "941100"] [msg "XSS Attack Detected via libinjection"] [data "Matched Data: XSS data found within ARGS🆔 <script>"] [severity "CRITICAL"] [ver "OWASP_CRS/4.4.0-dev"] [tag "application-multi"] [tag "language-multi"] [tag "platform-multi"] [tag "attack-xss"] [tag "xss-perf-disable"] [tag "paranoia-level/1"] [tag "OWASP_CRS"] [tag "capec/1000/152/242"] [hostname "www.test.com"] [uri "/a/index.html"] [unique_id "ZmkQLMRnhk_2RbFR9ZGHggAAAJI"]

[Wed Jun 12 11:05:46.047957 2024] [security2:error] [pid 97790:tid 139691286275840] [client 10.16.18.12:49213] [client 10.16.18.12] ModSecurity: Access denied using proxy to (phase 2) http://www.test1.com/a/. detected XSS using libinjection. [file "/www/server/apache/conf/modsecurity/rules/REQUEST-941-APPLICATION-ATTACK-XSS.conf"] [line "100"] [id "941100"] [msg "XSS Attack Detected via libinjection"] [data "Matched Data: XSS data found within ARGS🆔 <script>"] [severity "CRITICAL"] [ver "OWASP_CRS/4.4.0-dev"] [tag "application-multi"] [tag "language-multi"] [tag "platform-multi"] [tag "attack-xss"] [tag "xss-perf-disable"] [tag "paranoia-level/1"] [tag "OWASP_CRS"] [tag "capec/1000/152/242"] [hostname "www.test.com"] [uri "/a/"] [unique_id "ZmkQijzeTyiVCq1qyoYiawAAANA"]

To Reproduce

Steps to reproduce the behavior:
curl http://www.test.com/a/index.html?id=<script>
curl http://www.test.com/a/?id=<script>

Expected behavior

If access a directory, it also can be forwarded.

Server (please complete the following information):

• ModSecurity version (and connector): ModSecurity v2.9.7
• WebServer: Apache 2.4.58
• OS (and distro): CentOS 7.9.2009 x86_64

Rule Set (please complete the following information):

• Running any public or commercial rule set? OWASP CRS
• What is the version number? ver.4.4.0-dev

Additional context

The SecDefaultAction configuration is as follows:
SecDefaultAction "phase:1,log,noauditlog,proxy:'[nocanon]http://www.test1.com%{REQUEST_FILENAME}'"
SecDefaultAction "phase:2,log,noauditlog,proxy:'[nocanon]http://www.test1.com%{REQUEST_FILENAME}'"

Start with the SecDefaultAction proxy configurations and reproduce both requests using the supplied curl commands against Apache 2.4.58 with ModSecurity v2.9.7 and OWASP CRS 4.4.0-dev. Compare proxy handling for /a/index.html and /a/; done means directory requests are forwarded as expected without breaking the reported rule behavior.