diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index e072d2a6..282b7910 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -37,12 +37,24 @@ jobs:
       - name: Linter (gradle)
         run: ./gradlew ktlintCheck
 
+      - name: Android lint (gradle)
+        run: ./gradlew lint --no-daemon
+
       - name: Test (gradle)
         run: ./gradlew test --no-daemon
 
+      - name: Python security regressions
+        run: |
+          if [ -d tests ]; then
+            python3 -m unittest discover -s tests -p 'test_*.py' -v
+          fi
+
       - name: Build APK (gradle)
         run: ./gradlew assembleDebug --no-daemon
 
+      - name: Build free release APK (gradle)
+        run: ./gradlew :app:assembleFreeRelease --no-daemon
+
       - name: Upload APK
         uses: actions/upload-artifact@v7
         with:
diff --git a/app/src/main/java/com/greenart7c3/nostrsigner/service/WebDavService.kt b/app/src/main/java/com/greenart7c3/nostrsigner/service/WebDavService.kt
index c4002c65..57c54bab 100644
--- a/app/src/main/java/com/greenart7c3/nostrsigner/service/WebDavService.kt
+++ b/app/src/main/java/com/greenart7c3/nostrsigner/service/WebDavService.kt
@@ -1,9 +1,11 @@
 package com.greenart7c3.nostrsigner.service
 
-import com.greenart7c3.nostrsigner.okhttp.TaggedSocketFactory
+import com.greenart7c3.nostrsigner.Amber
+import com.greenart7c3.nostrsigner.models.TorMode
+import com.greenart7c3.nostrsigner.okhttp.HttpClientManager
 import java.io.IOException
+import java.net.Proxy
 import java.util.concurrent.TimeUnit
-import javax.net.SocketFactory
 import okhttp3.Credentials
 import okhttp3.MediaType.Companion.toMediaType
 import okhttp3.OkHttpClient
@@ -13,12 +15,19 @@ import okhttp3.RequestBody.Companion.toRequestBody
 object WebDavService {
     private val MEDIA_TYPE = "application/octet-stream".toMediaType()
 
-    private fun createClient(): OkHttpClient = OkHttpClient.Builder()
-        .connectTimeout(30, TimeUnit.SECONDS)
-        .readTimeout(60, TimeUnit.SECONDS)
-        .writeTimeout(60, TimeUnit.SECONDS)
-        .socketFactory(TaggedSocketFactory(SocketFactory.getDefault()))
-        .build()
+    private fun createClient(): OkHttpClient {
+        check(Amber.instance.isSettingsLoaded) { "Network settings are not loaded yet" }
+        val useProxy = Amber.instance.settings.torMode != TorMode.DISABLED
+        val client = HttpClientManager.getHttpClient(useProxy)
+        check(!useProxy || client.proxy?.type() == Proxy.Type.SOCKS) { "Tor proxy is not configured yet" }
+        return client.newBuilder()
+            .connectTimeout(30, TimeUnit.SECONDS)
+            .readTimeout(60, TimeUnit.SECONDS)
+            .writeTimeout(60, TimeUnit.SECONDS)
+            .followRedirects(false)
+            .followSslRedirects(false)
+            .build()
+    }
 
     fun uploadFile(
         serverUrl: String,
@@ -27,6 +36,7 @@ object WebDavService {
         fileName: String,
         content: String,
     ): Result<Unit> = try {
+        WebDavTransportPolicy.requireSecureServerUrl(serverUrl)
         val client = createClient()
         val url = serverUrl.trimEnd('/') + "/" + fileName
         val credential = Credentials.basic(username, password)
@@ -54,6 +64,7 @@ object WebDavService {
         password: String,
         fileName: String,
     ): Result<String> = try {
+        WebDavTransportPolicy.requireSecureServerUrl(serverUrl)
         val client = createClient()
         val url = serverUrl.trimEnd('/') + "/" + fileName
         val credential = Credentials.basic(username, password)
@@ -82,6 +93,7 @@ object WebDavService {
         username: String,
         password: String,
     ): Result<Unit> = try {
+        WebDavTransportPolicy.requireSecureServerUrl(serverUrl)
         val client = createClient()
         val url = serverUrl.trimEnd('/')
         val credential = Credentials.basic(username, password)
diff --git a/app/src/main/java/com/greenart7c3/nostrsigner/service/WebDavTransportPolicy.kt b/app/src/main/java/com/greenart7c3/nostrsigner/service/WebDavTransportPolicy.kt
new file mode 100644
index 00000000..c8e096f3
--- /dev/null
+++ b/app/src/main/java/com/greenart7c3/nostrsigner/service/WebDavTransportPolicy.kt
@@ -0,0 +1,15 @@
+package com.greenart7c3.nostrsigner.service
+
+import java.net.URI
+
+object WebDavTransportPolicy {
+    fun requireSecureServerUrl(serverUrl: String) {
+        val uri = URI(serverUrl)
+        require(uri.scheme.equals("https", ignoreCase = true) && !uri.host.isNullOrBlank()) {
+            "WebDAV requires an HTTPS server URL"
+        }
+        require(uri.userInfo == null && uri.query == null && uri.fragment == null) {
+            "WebDAV server URLs must not contain credentials, a query, or a fragment"
+        }
+    }
+}
diff --git a/app/src/test/java/com/greenart7c3/nostrsigner/service/WebDavTransportPolicyTest.kt b/app/src/test/java/com/greenart7c3/nostrsigner/service/WebDavTransportPolicyTest.kt
new file mode 100644
index 00000000..26212422
--- /dev/null
+++ b/app/src/test/java/com/greenart7c3/nostrsigner/service/WebDavTransportPolicyTest.kt
@@ -0,0 +1,18 @@
+package com.greenart7c3.nostrsigner.service
+
+import org.junit.Assert.assertThrows
+import org.junit.Test
+
+class WebDavTransportPolicyTest {
+    @Test
+    fun `credentials cannot be sent to cleartext or ambiguous URLs`() {
+        listOf("http://backup.example", "https://user:pass@backup.example", "https://backup.example?token=secret", "https://backup.example#fragment").forEach {
+            assertThrows(IllegalArgumentException::class.java) { WebDavTransportPolicy.requireSecureServerUrl(it) }
+        }
+    }
+
+    @Test
+    fun `secure server with a base path is accepted`() {
+        WebDavTransportPolicy.requireSecureServerUrl("https://backup.example:8443/remote.php/dav/files/user")
+    }
+}