diff --git a/changelog.html b/changelog.html
index fad07088da..82d83c4b49 100644
--- a/changelog.html
+++ b/changelog.html
@@ -46,9 +46,11 @@ <h1>
 
 <p><b>1.12.1</b> (to be determined)</p>
 <ul>
+    <li>Now requires Openfire 5.1.0 or later</li>
     <li>[<a href="https://github.com/igniterealtime/openfire-restAPI-plugin/issues/259">#259</a>] - Prevent system property requests from affecting properties other than the one requested</li>
     <li>[<a href="https://github.com/igniterealtime/openfire-restAPI-plugin/issues/256">#256</a>] - Record configuration changes in audit log</li>
     <li>[<a href="https://github.com/igniterealtime/openfire-restAPI-plugin/issues/251">#251</a>] - Enable JUnit 5 tests</li>
+    <li>[<a href="https://github.com/igniterealtime/openfire-restAPI-plugin/issues/249">#249</a>] - Only trust forwarded headers (such as X-Forwarded-For) from trusted reverse proxies</li>
     <li>[<a href="https://github.com/igniterealtime/openfire-restAPI-plugin/issues/248">#248</a>] - Do not expose properties that are encrypted or otherwise sensitive.</li>
     <li>[<a href="https://github.com/igniterealtime/openfire-restAPI-plugin/issues/246">#246</a>] - Require custom authenticator plugin to be annotated as an authenticator</li>
     <li>[<a href="https://github.com/igniterealtime/openfire-restAPI-plugin/issues/244">#244</a>] - Prevent REST API plugin from exposing its own configuration (including authentication) via its own endpoints</li>
diff --git a/plugin.xml b/plugin.xml
index 73a7ca070d..4200247dfa 100644
--- a/plugin.xml
+++ b/plugin.xml
@@ -7,7 +7,7 @@
     <author>Roman Soldatow</author>
     <version>${project.version}</version>
     <date>2026-09-24</date>
-    <minServerVersion>5.0.0</minServerVersion>
+    <minServerVersion>5.1.0</minServerVersion>
     <adminconsole>
         <tab id="tab-server">
             <sidebar id="sidebar-server-settings">
diff --git a/pom.xml b/pom.xml
index e00ea4f168..067c625f40 100644
--- a/pom.xml
+++ b/pom.xml
@@ -4,7 +4,7 @@
     <parent>
         <artifactId>plugins</artifactId>
         <groupId>org.igniterealtime.openfire</groupId>
-        <version>5.0.0</version>
+        <version>5.1.0</version>
     </parent>
     <groupId>org.igniterealtime.openfire.plugins</groupId>
     <artifactId>restAPI</artifactId>
diff --git a/readme.md b/readme.md
index 376f127e5c..111c96c387 100644
--- a/readme.md
+++ b/readme.md
@@ -108,6 +108,30 @@ The third requirement cannot be verified automatically and is the implementer's
 implements the interface and carries the annotation, but returns without calling `abortWith(...)` on an
 unauthenticated request, will be loaded successfully and will silently grant unauthenticated access.
 
+### Restricting access by IP address
+
+Access to the REST API can additionally be limited to a list of allowed IP addresses. This is configured in the
+Openfire Admin console under Server > Server Settings > REST API (backed by the `plugin.restapi.allowedIPs` system
+property). When the list is empty, requests from any IP address are accepted.
+
+The plugin checks the IP address of the peer that is directly connected to Openfire. It does not itself inspect
+headers like `X-Forwarded-For`, as these can be set to arbitrary values by any client. When the REST API is accessed
+through a reverse proxy, configure Openfire's admin console to use the forwarded client address instead: enable
+`adminConsole.forwarded.enabled`, and list the IP addresses (or ranges) of your proxies in
+`adminConsole.forwarded.trusted.proxies`. Both can be set on the Admin Console Access page (Server > Server
+Manager > Admin Console Access). Openfire then uses forwarded headers only on requests that come from one of those
+trusted proxies.
+
+Be aware of the following:
+
+- When `adminConsole.forwarded.enabled` is `true` but no trusted proxies are configured, Openfire uses forwarded
+  headers from _any_ peer. Any client can then bypass the IP address check by sending a forged header. The REST API
+  shows a warning on its admin console page when it detects this configuration.
+- Make sure that your reverse proxy _replaces_ any `Forwarded` or `X-Forwarded-For` header that it receives from the
+  client, instead of appending to it. Otherwise, a value provided by the client can still end up being used as the
+  client's address.
+- Changes to the `adminConsole.forwarded.*` properties take effect only after the admin console has been restarted.
+
 # User related REST Endpoints
 
 ## Retrieve users
diff --git a/src/java/org/jivesoftware/openfire/plugin/rest/AuthFilter.java b/src/java/org/jivesoftware/openfire/plugin/rest/AuthFilter.java
index 561475930d..7a5b1ef809 100644
--- a/src/java/org/jivesoftware/openfire/plugin/rest/AuthFilter.java
+++ b/src/java/org/jivesoftware/openfire/plugin/rest/AuthFilter.java
@@ -84,17 +84,10 @@ public void filter(ContainerRequestContext containerRequest) throws IOException
         }
 
         if (!RESTServicePlugin.ALLOWED_IPS.getValue().isEmpty()) {
-            // Get client's IP address
-            String ipAddress = httpRequest.getHeader("x-forwarded-for");
-            if (ipAddress == null) {
-                ipAddress = httpRequest.getHeader("X_FORWARDED_FOR");
-                if (ipAddress == null) {
-                    ipAddress = httpRequest.getHeader("X-Forward-For");
-                    if (ipAddress == null) {
-                        ipAddress = httpRequest.getRemoteAddr();
-                    }
-                }
-            }
+            // Get client's IP address. Do not inspect headers like 'X-Forwarded-For' here: these can be spoofed by the client.
+            // When Openfire is configured to be accessed through a reverse proxy, its web server already replaces the remote
+            // address with the value from such headers, but only for requests from proxies that are configured to be trusted.
+            final String ipAddress = httpRequest.getRemoteAddr();
             if (!RESTServicePlugin.ALLOWED_IPS.getValue().contains(ipAddress)) {
                 LOG.warn("REST API rejected service for IP address: " + ipAddress);
                 throw new WebApplicationException(Status.UNAUTHORIZED);
diff --git a/src/java/org/jivesoftware/openfire/plugin/rest/RESTServicePlugin.java b/src/java/org/jivesoftware/openfire/plugin/rest/RESTServicePlugin.java
index b0b0d16c47..90a725330a 100644
--- a/src/java/org/jivesoftware/openfire/plugin/rest/RESTServicePlugin.java
+++ b/src/java/org/jivesoftware/openfire/plugin/rest/RESTServicePlugin.java
@@ -17,6 +17,7 @@
 package org.jivesoftware.openfire.plugin.rest;
 
 import org.jivesoftware.admin.AuthCheckFilter;
+import org.jivesoftware.openfire.container.AdminConsolePlugin;
 import org.jivesoftware.openfire.container.Plugin;
 import org.jivesoftware.openfire.container.PluginManager;
 import org.jivesoftware.openfire.plugin.rest.service.JerseyWrapper;
@@ -148,6 +149,26 @@ public void destroyPlugin() {
         AuthCheckFilter.removeExclude(JerseyWrapper.SERVLET_URL);
     }
 
+    /**
+     * Checks if the IP addresses that are verified against {@link #ALLOWED_IPS} can be controlled by the client.
+     *
+     * The REST API is served by the admin console's web server. When that is configured to use 'Forwarded' or
+     * 'X-Forwarded-For' style HTTP headers to determine the address of the client, but no trusted reverse proxies are
+     * configured, then these headers are honored when sent by any peer. In that case, any client can pretend to have
+     * an address that is on the list of allowed IP addresses.
+     *
+     * Note that changes to the admin console configuration only take effect after the admin console is restarted. This
+     * method evaluates the configured values, which may differ from the configuration that is currently in effect.
+     *
+     * @return true if a non-empty list of allowed IP addresses is configured that can be bypassed by spoofing headers.
+     */
+    public static boolean isAllowedIPsCheckSpoofable()
+    {
+        return !ALLOWED_IPS.getValue().isEmpty()
+            && AdminConsolePlugin.ADMIN_CONSOLE_FORWARDED.getValue()
+            && AdminConsolePlugin.ADMIN_CONSOLE_FORWARDED_TRUSTED_PROXIES.getValue().isEmpty();
+    }
+
     /**
      * Validates the custom authentication filter class name.
      *
diff --git a/src/java/org/jivesoftware/openfire/plugin/rest/service/UserServiceLegacy.java b/src/java/org/jivesoftware/openfire/plugin/rest/service/UserServiceLegacy.java
index 4ce5db4e5c..157c78a99e 100644
--- a/src/java/org/jivesoftware/openfire/plugin/rest/service/UserServiceLegacy.java
+++ b/src/java/org/jivesoftware/openfire/plugin/rest/service/UserServiceLegacy.java
@@ -74,17 +74,10 @@ public Response userSerivceRequest() throws IOException {
         PrintWriter out = response.getWriter();
 
         if (!RESTServicePlugin.ALLOWED_IPS.getValue().isEmpty()) {
-            // Get client's IP address
-            String ipAddress = request.getHeader("x-forwarded-for");
-            if (ipAddress == null) {
-                ipAddress = request.getHeader("X_FORWARDED_FOR");
-                if (ipAddress == null) {
-                    ipAddress = request.getHeader("X-Forward-For");
-                    if (ipAddress == null) {
-                        ipAddress = request.getRemoteAddr();
-                    }
-                }
-            }
+            // Get client's IP address. Do not inspect headers like 'X-Forwarded-For' here: these can be spoofed by the client.
+            // When Openfire is configured to be accessed through a reverse proxy, its web server already replaces the remote
+            // address with the value from such headers, but only for requests from proxies that are configured to be trusted.
+            final String ipAddress = request.getRemoteAddr();
             if (!RESTServicePlugin.ALLOWED_IPS.getValue().contains(ipAddress)) {
                 LOG.warn("User service rejected service to IP address: " + ipAddress);
                 replyError("RequestNotAuthorised", response, out);
diff --git a/src/web/images/warning-16x16.gif b/src/web/images/warning-16x16.gif
new file mode 100644
index 0000000000..15ba374c5e
Binary files /dev/null and b/src/web/images/warning-16x16.gif differ
diff --git a/src/web/rest-api.jsp b/src/web/rest-api.jsp
index ed660fe733..9f0d090952 100644
--- a/src/web/rest-api.jsp
+++ b/src/web/rest-api.jsp
@@ -112,9 +112,6 @@
 </head>
 <body>
 
-    <p>Use the form below to enable or disable the REST API and
-        configure the authentication.</p>
-
     <%
         if (success) {
     %>
@@ -136,6 +133,29 @@
         }
     %>
     
+    <%
+        if (RESTServicePlugin.isAllowedIPsCheckSpoofable()) {
+    %>
+    <div class="jive-warning">
+        <table cellpadding="0" cellspacing="0" border="0">
+            <tbody>
+            <tr>
+                <td class="jive-icon"><img src="images/warning-16x16.gif"
+                                           width="16" height="16" border="0"></td>
+                <td class="jive-icon-label">Access is restricted to specific IP addresses, but the admin console is
+                    configured to determine the client address from forwarded HTTP headers (such as X-Forwarded-For),
+                    without a list of trusted proxies. Any client can bypass the IP address check by sending such a header.
+                    Configure the addresses of your reverse proxies as trusted proxies on the
+                    <a href="../../system-admin-console-access.jsp">Admin Console Access</a> page.
+                </td>
+            </tr>
+            </tbody>
+        </table>
+    </div>
+    <br>
+    <%
+        }
+    %>
     <%  
         if (errors.get("loadingStatus") != null) { 
     %>
@@ -175,6 +195,9 @@
         }
     %>
 
+    <p>Use the form below to enable or disable the REST API and
+        configure the authentication.</p>
+
     <form action="rest-api.jsp?save" method="post">
 
         <fieldset>
@@ -230,6 +253,7 @@
 
                     <label for="allowedIPs">Allowed IP Addresses:</label>
                     <textarea name="allowedIPs" cols="40" rows="3" wrap="virtual"><%=((allowedIPs != null) ? allowedIPs : "")%></textarea>
+                    <div style="margin-left: 20px; margin-top: 5px;">Note: when the REST API is accessed through a reverse proxy, configure Openfire to use the forwarded client address, and to trust only your proxies, on the <a href="../../system-admin-console-access.jsp">Admin Console Access</a> page.</div>
                     <br>
                     <br>