diff --git a/client/html/tag_edit.tpl b/client/html/tag_edit.tpl
index 65bd187..e57ac79 100644
--- a/client/html/tag_edit.tpl
+++ b/client/html/tag_edit.tpl
@@ -3,23 +3,51 @@
         <div class='input'>
             <ul>
                 <li class='names'>
-                    <%= ctx.makeTextInput({text: 'Names', value: ctx.tag.names.join(' '), required: true, readonly: !ctx.canEditNames}) %>
+                    <% if (ctx.canEditNames) { %>
+                        <%= ctx.makeTextInput({
+                            text: 'Names',
+                            value: ctx.tag.names.join(' '),
+                            required: true,
+                        }) %>
+                    <% } %>
                 </li>
                 <li class='category'>
-                    <%= ctx.makeSelect({text: 'Category', keyValues: ctx.categories, selectedKey: ctx.tag.category, required: true, readonly: !ctx.canEditCategory}) %>
+                    <% if (ctx.canEditCategory) { %>
+                        <%= ctx.makeSelect({
+                            text: 'Category',
+                            keyValues: ctx.categories,
+                            selectedKey: ctx.tag.category,
+                            required: true,
+                        }) %>
+                    <% } %>
                 </li>
                 <li class='implications'>
-                    <%= ctx.makeTextInput({text: 'Implications', value: ctx.tag.implications.join(' '), readonly: !ctx.canEditImplications}) %>
+                    <% if (ctx.canEditImplications) { %>
+                        <%= ctx.makeTextInput({
+                            text: 'Implications',
+                            value: ctx.tag.implications.join(' '),
+                        }) %>
+                    <% } %>
                 </li>
                 <li class='suggestions'>
-                    <%= ctx.makeTextInput({text: 'Suggestions', value: ctx.tag.suggestions.join(' '), readonly: !ctx.canEditSuggestions}) %>
+                    <% if (ctx.canEditSuggestions) { %>
+                        <%= ctx.makeTextInput({
+                            text: 'Suggestions',
+                            value: ctx.tag.suggestions.join(' '),
+                        }) %>
+                    <% } %>
                 </li>
                 <li class='description'>
-                    <%= ctx.makeTextarea({text: 'Description', value: ctx.tag.description, readonly: !ctx.canEditDescription}) %>
+                    <% if (ctx.canEditDescription) { %>
+                        <%= ctx.makeTextarea({
+                            text: 'Description',
+                            value: ctx.tag.description,
+                        }) %>
+                    <% } %>
                 </li>
             </ul>
         </div>
-        <% if (ctx.canEditNames || ctx.canEditCategory || ctx.canEditImplications || ctx.canEditSuggestions) { %>
+        <% if (ctx.canEditAnything) { %>
             <div class='messages'></div>
             <div class='buttons'>
                 <input type='submit' class='save' value='Save changes'>
diff --git a/client/js/controllers/tag_controller.js b/client/js/controllers/tag_controller.js
index 0f8dfae..1eaca6f 100644
--- a/client/js/controllers/tag_controller.js
+++ b/client/js/controllers/tag_controller.js
@@ -25,6 +25,7 @@ class TagController {
             this._view = new TagView({
                 tag: tag,
                 section: section,
+                canEditAnything: api.hasPrivilege('tags:edit'),
                 canEditNames: api.hasPrivilege('tags:edit:names'),
                 canEditCategory: api.hasPrivilege('tags:edit:category'),
                 canEditImplications: api.hasPrivilege('tags:edit:implications'),
@@ -53,11 +54,21 @@ class TagController {
     _evtChange(e) {
         this._view.clearMessages();
         this._view.disableForm();
-        e.detail.tag.names = e.detail.names;
-        e.detail.tag.category = e.detail.category;
-        e.detail.tag.implications = e.detail.implications;
-        e.detail.tag.suggestions = e.detail.suggestions;
-        e.detail.tag.description = e.detail.description;
+        if (e.detail.names !== undefined) {
+            e.detail.tag.names = e.detail.names;
+        }
+        if (e.detail.category !== undefined) {
+            e.detail.tag.category = e.detail.category;
+        }
+        if (e.detail.implications !== undefined) {
+            e.detail.tag.implications = e.detail.implications;
+        }
+        if (e.detail.suggestions !== undefined) {
+            e.detail.tag.suggestions = e.detail.suggestions;
+        }
+        if (e.detail.description !== undefined) {
+            e.detail.tag.description = e.detail.description;
+        }
         e.detail.tag.save().then(() => {
             this._view.showSuccess('Tag saved.');
             this._view.enableForm();
diff --git a/client/js/models/post.js b/client/js/models/post.js
index 16d11ca..fb60683 100644
--- a/client/js/models/post.js
+++ b/client/js/models/post.js
@@ -4,12 +4,7 @@ const api = require('../api.js');
 const tags = require('../tags.js');
 const events = require('../events.js');
 const CommentList = require('./comment_list.js');
-
-function _arraysDiffer(source1, source2) {
-    return (
-        [...source1].filter(value => !source2.includes(value)).length > 0 ||
-        [...source2].filter(value => !source1.includes(value)).length > 0);
-}
+const misc = require('../util/misc.js');
 
 class Post extends events.EventTarget {
     constructor() {
@@ -111,13 +106,13 @@ class Post extends events.EventTarget {
         if (this._safety !== this._orig._safety) {
             detail.safety = this._safety;
         }
-        if (_arraysDiffer(this._flags, this._orig._flags)) {
+        if (misc.arraysDiffer(this._flags, this._orig._flags)) {
             detail.flags = this._flags;
         }
-        if (_arraysDiffer(this._tags, this._orig._tags)) {
+        if (misc.arraysDiffer(this._tags, this._orig._tags)) {
             detail.tags = this._tags;
         }
-        if (_arraysDiffer(this._relations, this._orig._relations)) {
+        if (misc.arraysDiffer(this._relations, this._orig._relations)) {
             detail.relations = this._relations;
         }
 
diff --git a/client/js/models/tag.js b/client/js/models/tag.js
index 8d65141..32db964 100644
--- a/client/js/models/tag.js
+++ b/client/js/models/tag.js
@@ -2,16 +2,21 @@
 
 const api = require('../api.js');
 const events = require('../events.js');
+const misc = require('../util/misc.js');
 
 class Tag extends events.EventTarget {
     constructor() {
         super();
+        this._orig         = {};
+
         this._origName     = null;
-        this._names        = null;
         this._category     = null;
         this._description  = null;
-        this._suggestions  = null;
-        this._implications = null;
+
+        this._names        = [];
+        this._suggestions  = [];
+        this._implications = [];
+
         this._postCount    = null;
         this._creationTime = null;
         this._lastEditTime = null;
@@ -48,13 +53,25 @@ class Tag extends events.EventTarget {
     }
 
     save() {
-        const detail = {
-            names: this.names,
-            category: this.category,
-            description: this.description,
-            implications: this.implications,
-            suggestions: this.suggestions,
-        };
+        const detail = {};
+
+        // send only changed fields to avoid user privilege violation
+        if (misc.arraysDiffer(this._names, this._orig._names)) {
+            detail.names = this._names;
+        }
+        if (this._category !== this._orig._category) {
+            detail.category = this._category;
+        }
+        if (this._description !== this._orig._description) {
+            detail.description = this._description;
+        }
+        if (misc.arraysDiffer(this._implications, this._orig._implications)) {
+            detail.implications = this._implications;
+        }
+        if (misc.arraysDiffer(this._suggestions, this._orig._suggestions)) {
+            detail.suggestions = this._suggestions;
+        }
+
         let promise = this._origName ?
             api.put('/tag/' + this._origName, detail) :
             api.post('/tags', detail);
@@ -104,15 +121,20 @@ class Tag extends events.EventTarget {
     }
 
     _updateFromResponse(response) {
-        this._origName     = response.names ? response.names[0] : null;
-        this._names        = response.names;
-        this._category     = response.category;
-        this._description  = response.description;
-        this._implications = response.implications;
-        this._suggestions  = response.suggestions;
-        this._creationTime = response.creationTime;
-        this._lastEditTime = response.lastEditTime;
-        this._postCount    = response.usages;
+        const map = {
+            _origName:     response.names ? response.names[0] : null,
+            _names:        response.names,
+            _category:     response.category,
+            _description:  response.description,
+            _implications: response.implications,
+            _suggestions:  response.suggestions,
+            _creationTime: response.creationTime,
+            _lastEditTime: response.lastEditTime,
+            _postCount:    response.usages,
+        };
+
+        Object.assign(this, map);
+        Object.assign(this._orig, map);
     }
 };
 
diff --git a/client/js/util/misc.js b/client/js/util/misc.js
index 7bcd632..4bf0e1a 100644
--- a/client/js/util/misc.js
+++ b/client/js/util/misc.js
@@ -244,6 +244,12 @@ function escapeHtml(unsafe) {
         .replace(/'/g, '&apos;');
 }
 
+function arraysDiffer(source1, source2) {
+    return (
+        [...source1].filter(value => !source2.includes(value)).length > 0 ||
+        [...source2].filter(value => !source1.includes(value)).length > 0);
+}
+
 module.exports = {
     range: range,
     formatUrlParameters: formatUrlParameters,
@@ -259,4 +265,5 @@ module.exports = {
     escapeHtml: escapeHtml,
     makeCssName: makeCssName,
     splitByWhitespace: splitByWhitespace,
+    arraysDiffer: arraysDiffer,
 };
diff --git a/client/js/views/tag_edit_view.js b/client/js/views/tag_edit_view.js
index 35e0e8a..515b4ad 100644
--- a/client/js/views/tag_edit_view.js
+++ b/client/js/views/tag_edit_view.js
@@ -79,13 +79,26 @@ class TagEditView extends events.EventTarget {
         this.dispatchEvent(new CustomEvent('submit', {
             detail: {
                 tag: this._tag,
-                names: misc.splitByWhitespace(this._namesFieldNode.value),
-                category: this._categoryFieldNode.value,
-                implications: misc.splitByWhitespace(
-                    this._implicationsFieldNode.value),
-                suggestions: misc.splitByWhitespace(
-                    this._suggestionsFieldNode.value),
-                description: this._descriptionFieldNode.value,
+
+                names: this._namesFieldNode ?
+                    misc.splitByWhitespace(this._namesFieldNode.value) :
+                    undefined,
+
+                category: this._categoryFieldNode ?
+                    this._categoryFieldNode.value :
+                    undefined,
+
+                implications: this._implicationsFieldNode ?
+                    misc.splitByWhitespace(this._implicationsFieldNode.value) :
+                    undefined,
+
+                suggestions: this._suggestionsFieldNode ?
+                    misc.splitByWhitespace(this._suggestionsFieldNode.value) :
+                    undefined,
+
+                description: this._descriptionFieldNode ?
+                    this._descriptionFieldNode.value :
+                    undefined,
             },
         }));
     }