diff --git a/scripts/repository/commit_hook.php b/scripts/repository/commit_hook.php
index 4f6997c52a..44c772225c 100755
--- a/scripts/repository/commit_hook.php
+++ b/scripts/repository/commit_hook.php
@@ -54,10 +54,62 @@ if (!$repository->isHosted()) {
 
 $engine->setRepository($repository);
 
+$args = new PhutilArgumentParser($argv);
+$args->parsePartial(
+  array(
+    array(
+      'name' => 'hook-mode',
+      'param' => 'mode',
+      'help' => pht('Hook execution mode.'),
+    ),
+  ));
+
+$argv = array_merge(
+  array($argv[0]),
+  $args->getUnconsumedArgumentVector());
 
 // Figure out which user is writing the commit.
+$hook_mode = $args->getArg('hook-mode');
+if ($hook_mode !== null) {
+  $known_modes = array(
+    'svn-revprop' => true,
+  );
 
-if ($repository->isGit() || $repository->isHg()) {
+  if (empty($known_modes[$hook_mode])) {
+    throw new Exception(
+      pht(
+        'Invalid Hook Mode: This hook was invoked in "%s" mode, but this '.
+        'is not a recognized hook mode. Valid modes are: %s.',
+        $hook_mode,
+        implode(', ', array_keys($known_modes))));
+  }
+}
+
+$is_svnrevprop = ($hook_mode == 'svn-revprop');
+
+if ($is_svnrevprop) {
+  // For now, we let these through if the repository allows dangerous changes
+  // and prevent them if it doesn't. See T11208 for discussion.
+
+  $revprop_key = $argv[5];
+
+  if ($repository->shouldAllowDangerousChanges()) {
+    $err = 0;
+  } else {
+    $err = 1;
+
+    $console = PhutilConsole::getConsole();
+    $console->writeErr(
+      pht(
+        "DANGEROUS CHANGE: Dangerous change protection is enabled for this ".
+        "repository, so you can not change revision properties (you are ".
+        "attempting to edit \"%s\").\n".
+        "Edit the repository configuration before making dangerous changes.",
+        $revprop_key));
+  }
+
+  exit($err);
+} else if ($repository->isGit() || $repository->isHg()) {
   $username = getenv(DiffusionCommitHookEngine::ENV_USER);
   if (!strlen($username)) {
     throw new Exception(
diff --git a/src/applications/diffusion/controller/DiffusionRepositoryEditDangerousController.php b/src/applications/diffusion/controller/DiffusionRepositoryEditDangerousController.php
index d0dd2cc2e9..1088733cfc 100644
--- a/src/applications/diffusion/controller/DiffusionRepositoryEditDangerousController.php
+++ b/src/applications/diffusion/controller/DiffusionRepositoryEditDangerousController.php
@@ -18,25 +18,14 @@ final class DiffusionRepositoryEditDangerousController
       ->getPanelURI();
 
     if (!$repository->canAllowDangerousChanges()) {
-      if ($repository->isSVN()) {
-        return $this->newDialog()
-          ->setTitle(pht('Not in Danger'))
-          ->appendParagraph(
-            pht(
-              'It is not possible for users to push any dangerous changes '.
-              'to a Subversion repository. Pushes to a Subversion repository '.
-              'can always be reverted and never destroy data.'))
-          ->addCancelButton($panel_uri);
-      } else {
-        return $this->newDialog()
-          ->setTitle(pht('Unprotectable Repository'))
-          ->appendParagraph(
-            pht(
-              'This repository can not be protected from dangerous changes '.
-              'because Phabricator does not control what users are allowed '.
-              'to push to it.'))
-          ->addCancelButton($panel_uri);
-      }
+      return $this->newDialog()
+        ->setTitle(pht('Unprotectable Repository'))
+        ->appendParagraph(
+          pht(
+            'This repository can not be protected from dangerous changes '.
+            'because Phabricator does not control what users are allowed '.
+            'to push to it.'))
+        ->addCancelButton($panel_uri);
     }
 
     if ($request->isFormPost()) {
@@ -57,18 +46,34 @@ final class DiffusionRepositoryEditDangerousController
 
     if ($repository->shouldAllowDangerousChanges()) {
       $title = pht('Prevent Dangerous Changes');
-      $body = pht(
-        'It will no longer be possible to delete branches from this '.
-        'repository, or %s push to this repository.',
-        $force);
+
+      if ($repository->isSVN()) {
+        $body = pht(
+          'It will no longer be possible to edit revprops in this '.
+          'repository.');
+      } else {
+        $body = pht(
+          'It will no longer be possible to delete branches from this '.
+          'repository, or %s push to this repository.',
+          $force);
+      }
+
       $submit = pht('Prevent Dangerous Changes');
     } else {
       $title = pht('Allow Dangerous Changes');
-      $body = pht(
-        'If you allow dangerous changes, it will be possible to delete '.
-        'branches and %s push this repository. These operations can '.
-        'alter a repository in a way that is difficult to recover from.',
-        $force);
+      if ($repository->isSVN()) {
+        $body = pht(
+          'If you allow dangerous changes, it will be possible to edit '.
+          'reprops in this repository, including arbitrarily rewriting '.
+          'commit messages. These operations can alter a repository in a '.
+          'way that is difficult to recover from.');
+      } else {
+        $body = pht(
+          'If you allow dangerous changes, it will be possible to delete '.
+          'branches and %s push this repository. These operations can '.
+          'alter a repository in a way that is difficult to recover from.',
+          $force);
+      }
       $submit = pht('Allow Dangerous Changes');
     }
 
diff --git a/src/applications/repository/engine/PhabricatorRepositoryPullEngine.php b/src/applications/repository/engine/PhabricatorRepositoryPullEngine.php
index 7e54bf4620..08fe8ea224 100644
--- a/src/applications/repository/engine/PhabricatorRepositoryPullEngine.php
+++ b/src/applications/repository/engine/PhabricatorRepositoryPullEngine.php
@@ -191,7 +191,7 @@ final class PhabricatorRepositoryPullEngine
       ));
   }
 
-  private function installHook($path) {
+  private function installHook($path, array $hook_argv = array()) {
     $this->log('%s', pht('Installing commit hook to "%s"...', $path));
 
     $repository = $this->getRepository();
@@ -202,10 +202,11 @@ final class PhabricatorRepositoryPullEngine
 
     $full_php_path = Filesystem::resolveBinary('php');
     $cmd = csprintf(
-      'exec %s -f %s -- %s "$@"',
+      'exec %s -f %s -- %s %Ls "$@"',
       $full_php_path,
       $bin,
-      $identifier);
+      $identifier,
+      $hook_argv);
 
     $hook = "#!/bin/sh\nexport TERM=dumb\n{$cmd}\n";
 
@@ -585,8 +586,16 @@ final class PhabricatorRepositoryPullEngine
     $root = $repository->getLocalPath();
 
     $path = '/hooks/pre-commit';
-
     $this->installHook($root.$path);
+
+    $revprop_path = '/hooks/pre-revprop-change';
+
+    $revprop_argv = array(
+      '--hook-mode',
+      'svn-revprop',
+    );
+
+    $this->installHook($root.$revprop_path, $revprop_argv);
   }
 
 
diff --git a/src/applications/repository/storage/PhabricatorRepository.php b/src/applications/repository/storage/PhabricatorRepository.php
index d0f3f9f4d8..4a7e3d4681 100644
--- a/src/applications/repository/storage/PhabricatorRepository.php
+++ b/src/applications/repository/storage/PhabricatorRepository.php
@@ -1623,11 +1623,10 @@ final class PhabricatorRepository extends PhabricatorRepositoryDAO
       return false;
     }
 
-    if ($this->isGit() || $this->isHg()) {
-      return true;
-    }
+    // In Git and Mercurial, ref deletions and rewrites are dangerous.
+    // In Subversion, editing revprops is dangerous.
 
-    return false;
+    return true;
   }
 
   public function shouldAllowDangerousChanges() {