diff --git a/CHANGES b/CHANGES
index 59d4b0b123..4e3849af7b 100644
--- a/CHANGES
+++ b/CHANGES
@@ -44,6 +44,9 @@ Release 1.15.4 [PENDING]
     body.
     <https://github.com/jhy/jsoup/issues/1778>
 
+  * Bugfix: fixed an issue in Safelist.removeAttributes which could throw a ConcurrentModificationException when using
+    the ":all" pseudo-attribute.
+
   * Change: deprecated the unused Document#normalise() method. Normalization occurs during the HTML tree construction,
     and no longer as a distinct phase.
 
diff --git a/src/main/java/org/jsoup/safety/Safelist.java b/src/main/java/org/jsoup/safety/Safelist.java
index 289d555706..710c070e38 100644
--- a/src/main/java/org/jsoup/safety/Safelist.java
+++ b/src/main/java/org/jsoup/safety/Safelist.java
@@ -12,6 +12,7 @@ Thank you to Ryan Grove (wonko.com) for the Ruby HTML cleaner http://github.com/
 
 import java.util.HashMap;
 import java.util.HashSet;
+import java.util.Iterator;
 import java.util.Map;
 import java.util.Set;
 
@@ -63,6 +64,7 @@ XSS attack examples (that jsoup will safegaurd against the default Cleaner and S
  </p>
  */
 public class Safelist {
+    private static final String All = ":all";
     private final Set<TagName> tagNames; // tags allowed, lower case. e.g. [p, br, span]
     private final Map<TagName, Set<AttributeKey>> attributes; // tag -> attribute[]. allowed attributes [href] for a tag.
     private final Map<TagName, Map<AttributeKey, AttributeValue>> enforcedAttributes; // always set these attribute values
@@ -342,14 +344,16 @@ public Safelist removeAttributes(String tag, String... attributes) {
             if(currentSet.isEmpty()) // Remove tag from attribute map if no attributes are allowed for tag
                 this.attributes.remove(tagName);
         }
-        if(tag.equals(":all")) // Attribute needs to be removed from all individually set tags
-            for(TagName name: this.attributes.keySet()) {
-                Set<AttributeKey> currentSet = this.attributes.get(name);
+        if(tag.equals(All)) { // Attribute needs to be removed from all individually set tags
+            Iterator<Map.Entry<TagName, Set<AttributeKey>>> it = this.attributes.entrySet().iterator();
+            while (it.hasNext()) {
+                Map.Entry<TagName, Set<AttributeKey>> entry = it.next();
+                Set<AttributeKey> currentSet = entry.getValue();
                 currentSet.removeAll(attributeSet);
-
                 if(currentSet.isEmpty()) // Remove tag from attribute map if no attributes are allowed for tag
-                    this.attributes.remove(name);
+                    it.remove();
             }
+        }
         return this;
     }
 
@@ -555,7 +559,7 @@ protected boolean isSafeAttribute(String tagName, Element el, Attribute attr) {
             }
         }
         // no attributes defined for tag, try :all tag
-        return !tagName.equals(":all") && isSafeAttribute(":all", el, attr);
+        return !tagName.equals(All) && isSafeAttribute(All, el, attr);
     }
 
     private boolean testValidProtocol(Element el, Attribute attr, Set<Protocol> protocols) {
diff --git a/src/test/java/org/jsoup/safety/CleanerTest.java b/src/test/java/org/jsoup/safety/CleanerTest.java
index 8a03ed02dc..d7c6371cbc 100644
--- a/src/test/java/org/jsoup/safety/CleanerTest.java
+++ b/src/test/java/org/jsoup/safety/CleanerTest.java
@@ -67,6 +67,32 @@ public class CleanerTest {
         assertEquals("<p>Nice</p><blockquote>Hello</blockquote>", TextUtil.stripNewlines(cleanHtml));
     }
 
+    @Test void allAttributes() {
+        String h = "<div class=foo data=true><p class=bar>Text</p></div><blockquote cite='https://example.com'>Foo";
+        Safelist safelist = Safelist.relaxed();
+        safelist.addAttributes(":all", "class");
+        safelist.addAttributes("div", "data");
+
+        String clean1 = Jsoup.clean(h, safelist);
+        assertEquals("<div class=\"foo\" data=\"true\"><p class=\"bar\">Text</p></div><blockquote cite=\"https://example.com\">Foo</blockquote>", TextUtil.stripNewlines(clean1));
+
+        safelist.removeAttributes(":all", "class", "cite");
+
+        String clean2 = Jsoup.clean(h, safelist);
+        assertEquals("<div data=\"true\"><p>Text</p></div><blockquote>Foo</blockquote>", TextUtil.stripNewlines(clean2));
+    }
+
+    @Test void removeProtocols() {
+        String h = "<a href='any://example.com'>Link</a>";
+        Safelist safelist = Safelist.relaxed();
+        String clean1 = Jsoup.clean(h, safelist);
+        assertEquals("<a>Link</a>", clean1);
+
+        safelist.removeProtocols("a", "href", "ftp", "http", "https", "mailto");
+        String clean2 = Jsoup.clean(h, safelist); // all removed means any will work
+        assertEquals("<a href=\"any://example.com\">Link</a>", clean2);
+    }
+
     @Test public void testRemoveEnforcedAttributes() {
         String h = "<div><p><A HREF='HTTP://nice.com'>Nice</a></p><blockquote>Hello</blockquote>";
         String cleanHtml = Jsoup.clean(h, Safelist.basic().removeEnforcedAttribute("a", "rel"));