Plesk has scheduled the removal of XML-RPC API protocol versions 1.6.9.0 and earlier for Plesk Obsidian 18.0.82. They were deprecated in 18.0.80, and the Plesk feature deprecation plan lists 18.0.82 as the removal release. Once a server is on 18.0.82, any billing system, provisioning script, or monitoring tool that still sends an old version in its XML packets is expected to stop working.
As of 24 October 2026 the newest build in the Plesk change log is 18.0.81 Update 4, so there is still time to find the stragglers. This matters most if you provision Plesk hosting from WHMCS, Blesta, or your own code.
What changes in 18.0.82
| Up to 18.0.81 | 18.0.82 and later | |
|---|---|---|
Protocol 1.6.9.1, or no version attribute | Works | Works |
| Protocol 1.6.9.0 and earlier | Works, logs a deprecation warning | Planned for removal |
| REST API | Unaffected | Unaffected |
Plesk has logged a warning for requests older than 1.6.9.1 since 18.0.31, so the evidence is probably already on your servers. 18.0.81 is also the last release that supports Debian 11. If you still run Plesk on Debian 11, upgrade the server to Debian 12 as well.
Find integrations still using old versions
The warning lands in the panel log:
Protocol version '1.6.3.0' is deprecated. Current protocol version is '1.6.9.1'.
Count the versions in use on each server:
grep -o "Protocol version '[0-9.]*' is deprecated" /var/log/plesk/panel.log | sort | uniq -c
Then find which hosts are calling the XML API endpoint:
grep "/enterprise/control/agent.php" /var/log/plesk/httpsd_access_log | awk '{print $1}' | sort | uniq -c | sort -rn
Match each IP against your billing servers, monitoring hosts, and automation boxes. On older installations the same logs may be under /usr/local/psa/admin/logs/.
Fix the integration
For your own code, change the packet header:
<!-- before -->
<packet version="1.6.3.0">
<!-- after -->
<packet version="1.6.9.1">
Plesk's XML API docs also allow you to leave out the version attribute completely, in which case the latest protocol is used. That avoids hitting the same problem next time. Either way, test the operations you depend on, such as subscription creation, suspension, plan changes, and password resets. Some request and response elements changed between protocol versions.
For third-party billing modules, update the module and re-test provisioning against an 18.0.81 server. Plesk's own KB traced hourly 1.6.3.0 warnings to a WHMCS cron task on one customer server, and said the fix had to come from WHMCS. Check the current module before upgrading Plesk rather than assuming it is clean. The same applies to the Blesta Plesk module. If you are rewriting the integration anyway, consider moving it to the Plesk REST API, which resellers and customers can use since 18.0.79.
Restrict XML API access
While you're in there, limit who can reach the API. In /usr/local/psa/admin/conf/panel.ini:
[api]
allowedIPs = 203.0.113.10,203.0.113.11
Use commas with no surrounding spaces. If nothing uses the XML API, set enabled = off under [api] instead. Both settings also apply to the REST API.
Plesk also documents deprecationWarning = off under [api] to silence the warnings. Don't use it until the upgrade is done, because it hides the very log lines you need to find the remaining callers.
When will Plesk remove old XML-RPC protocol versions?+
How do I fix 'Protocol version is deprecated. Current protocol version is 1.6.9.1' in Plesk?+
Does the Plesk XML-RPC change affect WHMCS?+
Is the Plesk REST API affected by the XML-RPC removal?+
Can I keep using the Plesk XML API after 18.0.82?+
Next steps
- Set up Blesta provisioning for Plesk
- Configure the Plesk Firewall extension
- Fix Plesk update failures
You need an active Plesk license to receive 18.0.82 and the security builds that come before it.