### Author:  [@mentalstring](https://meta.discourse.org/u/mentalstring)
#### Post date: [July 14, 2022, 3:34pm UTC](https://meta.discourse.org/t/problem-with-post-revisions-after-updating-to-2-8-6-stable-or-2-9-0-beta7/232885/1 "2022-07-14T15:34:21Z")
We are noticing some posts where the previous revisions are not showing:
(there’s no text at all and notice the NaN on a post with 3 versions)
On the console I’m seeing a 500 error on `/posts/X/revisions/latest.json `.
On `/logs` I’m seeing the error below. This is on 2.8.6. We only noticed this after updating yesterday from 2.8.4, but I can’t guarantee it is related as we noticed this only in a couple of posts. I have tried rebuilt the container, but made no difference.
```plaintext
Psych::DisallowedClass (Tried to load unspecified class: Symbol)
app/serializers/post_revision_serializer.rb:233:in `block in all_revisions'
app/serializers/post_revision_serializer.rb:228:in `each'
app/serializers/post_revision_serializer.rb:228:in `all_revisions'
app/serializers/post_revision_serializer.rb:187:in `revisions'
app/serializers/post_revision_serializer.rb:254:in `previous'
app/serializers/post_revision_serializer.rb:50:in `previous_hidden'
(eval):5:in `_fast_attributes'
app/controllers/application_controller.rb:510:in `render_json_dump'
app/controllers/posts_controller.rb:425:in `latest_revision'
app/controllers/application_controller.rb:387:in `block in with_resolved_locale'
app/controllers/application_controller.rb:387:in `with_resolved_locale'
lib/middleware/omniauth_bypass_middleware.rb:71:in `call'
lib/content_security_policy/middleware.rb:12:in `call'
lib/middleware/anonymous_cache.rb:361:in `call'
config/initializers/100-quiet_logger.rb:23:in `call'
config/initializers/100-silence_logger.rb:31:in `call'
lib/middleware/enforce_hostname.rb:23:in `call'
lib/middleware/request_tracker.rb:198:in `call'
```
Backtrace:
```plaintext
/usr/local/lib/ruby/2.7.0/psych/class_loader.rb:97:in `find'
/usr/local/lib/ruby/2.7.0/psych/class_loader.rb:28:in `load'
/usr/local/lib/ruby/2.7.0/psych/class_loader.rb:39:in `block (2 levels) in '
/usr/local/lib/ruby/2.7.0/psych/class_loader.rb:32:in `symbolize'
/usr/local/lib/ruby/2.7.0/psych/class_loader.rb:82:in `symbolize'
/usr/local/lib/ruby/2.7.0/psych/scalar_scanner.rb:74:in `tokenize'
/usr/local/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:60:in `deserialize'
/usr/local/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:123:in `visit_Psych_Nodes_Scalar'
/usr/local/lib/ruby/2.7.0/psych/visitors/visitor.rb:16:in `visit'
/usr/local/lib/ruby/2.7.0/psych/visitors/visitor.rb:6:in `accept'
/usr/local/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:32:in `accept'
/usr/local/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:339:in `block in revive_hash'
/usr/local/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:338:in `each'
/usr/local/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:338:in `each_slice'
/usr/local/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:338:in `revive_hash'
/usr/local/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:162:in `visit_Psych_Nodes_Mapping'
/usr/local/lib/ruby/2.7.0/psych/visitors/visitor.rb:16:in `visit'
/usr/local/lib/ruby/2.7.0/psych/visitors/visitor.rb:6:in `accept'
/usr/local/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:32:in `accept'
/usr/local/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:332:in `block in register_empty'
/usr/local/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:332:in `each'
/usr/local/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:332:in `register_empty'
/usr/local/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:141:in `visit_Psych_Nodes_Sequence'
/usr/local/lib/ruby/2.7.0/psych/visitors/visitor.rb:16:in `visit'
/usr/local/lib/ruby/2.7.0/psych/visitors/visitor.rb:6:in `accept'
/usr/local/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:32:in `accept'
/usr/local/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:340:in `block in revive_hash'
/usr/local/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:338:in `each'
/usr/local/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:338:in `each_slice'
/usr/local/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:338:in `revive_hash'
/usr/local/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:162:in `visit_Psych_Nodes_Mapping'
/usr/local/lib/ruby/2.7.0/psych/visitors/visitor.rb:16:in `visit'
/usr/local/lib/ruby/2.7.0/psych/visitors/visitor.rb:6:in `accept'
/usr/local/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:32:in `accept'
/usr/local/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:313:in `visit_Psych_Nodes_Document'
/usr/local/lib/ruby/2.7.0/psych/visitors/visitor.rb:16:in `visit'
/usr/local/lib/ruby/2.7.0/psych/visitors/visitor.rb:6:in `accept'
/usr/local/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:32:in `accept'
/usr/local/lib/ruby/2.7.0/psych.rb:360:in `safe_load'
activerecord (6.1.6.1) lib/active_record/coders/yaml_column.rb:50:in `yaml_load'
activerecord (6.1.6.1) lib/active_record/coders/yaml_column.rb:26:in `load'
activerecord (6.1.6.1) lib/active_record/type/serialized.rb:22:in `deserialize'
activemodel (6.1.6.1) lib/active_model/type/helpers/mutable.rb:8:in `cast'
activemodel (6.1.6.1) lib/active_model/attribute.rb:175:in `type_cast'
activemodel (6.1.6.1) lib/active_model/attribute.rb:43:in `value'
activemodel (6.1.6.1) lib/active_model/attribute_set.rb:42:in `fetch_value'
activerecord (6.1.6.1) lib/active_record/attribute_methods/read.rb:36:in `_read_attribute'
activemodel (6.1.6.1) lib/active_model/attribute_methods.rb:254:in `modifications'
app/serializers/post_revision_serializer.rb:233:in `block in all_revisions'
app/serializers/post_revision_serializer.rb:228:in `each'
app/serializers/post_revision_serializer.rb:228:in `all_revisions'
app/serializers/post_revision_serializer.rb:187:in `revisions'
app/serializers/post_revision_serializer.rb:254:in `previous'
app/serializers/post_revision_serializer.rb:50:in `previous_hidden'
(eval):5:in `_fast_attributes'
active_model_serializers (0.8.4) lib/active_model/serializer.rb:456:in `attributes'
active_model_serializers (0.8.4) lib/active_model/serializer.rb:480:in `_serializable_hash'
active_model_serializers (0.8.4) lib/active_model/serializer.rb:359:in `serializable_hash'
active_model_serializers (0.8.4) lib/active_model/serializer.rb:347:in `as_json'
activesupport (6.1.6.1) lib/active_support/json/encoding.rb:22:in `encode'
activesupport (6.1.6.1) lib/active_support/json/encoding.rb:22:in `encode'
activesupport (6.1.6.1) lib/active_support/core_ext/object/json.rb:43:in `to_json'
active_model_serializers (0.8.4) lib/active_model/serializer.rb:331:in `to_json'
multi_json (1.15.0) lib/multi_json/adapters/oj.rb:56:in `dump'
multi_json (1.15.0) lib/multi_json/adapters/oj.rb:56:in `dump'
multi_json (1.15.0) lib/multi_json/adapter.rb:25:in `dump'
multi_json (1.15.0) lib/multi_json.rb:139:in `dump'
app/controllers/application_controller.rb:510:in `render_json_dump'
app/controllers/posts_controller.rb:425:in `latest_revision'
actionpack (6.1.6.1) lib/action_controller/metal/basic_implicit_render.rb:6:in `send_action'
actionpack (6.1.6.1) lib/abstract_controller/base.rb:228:in `process_action'
actionpack (6.1.6.1) lib/action_controller/metal/rendering.rb:30:in `process_action'
actionpack (6.1.6.1) lib/abstract_controller/callbacks.rb:42:in `block in process_action'
activesupport (6.1.6.1) lib/active_support/callbacks.rb:117:in `block in run_callbacks'
app/controllers/application_controller.rb:387:in `block in with_resolved_locale'
i18n (1.8.11) lib/i18n.rb:314:in `with_locale'
app/controllers/application_controller.rb:387:in `with_resolved_locale'
activesupport (6.1.6.1) lib/active_support/callbacks.rb:126:in `block in run_callbacks'
activesupport (6.1.6.1) lib/active_support/callbacks.rb:137:in `run_callbacks'
actionpack (6.1.6.1) lib/abstract_controller/callbacks.rb:41:in `process_action'
actionpack (6.1.6.1) lib/action_controller/metal/rescue.rb:22:in `process_action'
actionpack (6.1.6.1) lib/action_controller/metal/instrumentation.rb:34:in `block in process_action'
activesupport (6.1.6.1) lib/active_support/notifications.rb:203:in `block in instrument'
activesupport (6.1.6.1) lib/active_support/notifications/instrumenter.rb:24:in `instrument'
activesupport (6.1.6.1) lib/active_support/notifications.rb:203:in `instrument'
actionpack (6.1.6.1) lib/action_controller/metal/instrumentation.rb:33:in `process_action'
actionpack (6.1.6.1) lib/action_controller/metal/params_wrapper.rb:249:in `process_action'
activerecord (6.1.6.1) lib/active_record/railties/controller_runtime.rb:27:in `process_action'
actionpack (6.1.6.1) lib/abstract_controller/base.rb:165:in `process'
actionview (6.1.6.1) lib/action_view/rendering.rb:39:in `process'
rack-mini-profiler (2.3.3) lib/mini_profiler/profiling_methods.rb:111:in `block in profile_method'
actionpack (6.1.6.1) lib/action_controller/metal.rb:190:in `dispatch'
actionpack (6.1.6.1) lib/action_controller/metal.rb:254:in `dispatch'
actionpack (6.1.6.1) lib/action_dispatch/routing/route_set.rb:50:in `dispatch'
actionpack (6.1.6.1) lib/action_dispatch/routing/route_set.rb:33:in `serve'
actionpack (6.1.6.1) lib/action_dispatch/journey/router.rb:50:in `block in serve'
actionpack (6.1.6.1) lib/action_dispatch/journey/router.rb:32:in `each'
actionpack (6.1.6.1) lib/action_dispatch/journey/router.rb:32:in `serve'
actionpack (6.1.6.1) lib/action_dispatch/routing/route_set.rb:842:in `call'
lib/middleware/omniauth_bypass_middleware.rb:71:in `call'
rack (2.2.3) lib/rack/tempfile_reaper.rb:15:in `call'
rack (2.2.3) lib/rack/conditional_get.rb:27:in `call'
rack (2.2.3) lib/rack/head.rb:12:in `call'
actionpack (6.1.6.1) lib/action_dispatch/http/permissions_policy.rb:22:in `call'
lib/content_security_policy/middleware.rb:12:in `call'
lib/middleware/anonymous_cache.rb:361:in `call'
rack (2.2.3) lib/rack/session/abstract/id.rb:266:in `context'
rack (2.2.3) lib/rack/session/abstract/id.rb:260:in `call'
actionpack (6.1.6.1) lib/action_dispatch/middleware/cookies.rb:689:in `call'
actionpack (6.1.6.1) lib/action_dispatch/middleware/callbacks.rb:27:in `block in call'
activesupport (6.1.6.1) lib/active_support/callbacks.rb:98:in `run_callbacks'
actionpack (6.1.6.1) lib/action_dispatch/middleware/callbacks.rb:26:in `call'
actionpack (6.1.6.1) lib/action_dispatch/middleware/actionable_exceptions.rb:18:in `call'
actionpack (6.1.6.1) lib/action_dispatch/middleware/debug_exceptions.rb:29:in `call'
actionpack (6.1.6.1) lib/action_dispatch/middleware/show_exceptions.rb:33:in `call'
logster (2.10.1) lib/logster/middleware/reporter.rb:43:in `call'
railties
```
---
### Author:  [@david](https://meta.discourse.org/u/david)
#### Post date: [July 14, 2022, 3:49pm UTC](https://meta.discourse.org/t/problem-with-post-revisions-after-updating-to-2-8-6-stable-or-2-9-0-beta7/232885/2 "2022-07-14T15:49:03Z")
Is this a public site? Are you able to share a link to the affected posts? (via PM is fine if you prefer)
---
### Author:  [@mentalstring](https://meta.discourse.org/u/mentalstring)
#### Post date: [July 14, 2022, 3:52pm UTC](https://meta.discourse.org/t/problem-with-post-revisions-after-updating-to-2-8-6-stable-or-2-9-0-beta7/232885/3 "2022-07-14T15:52:23Z")
Sent via PM. Happy to send to others if needed.
---
### Author:  [@JammyDodger](https://meta.discourse.org/u/JammyDodger)
#### Post date: [July 14, 2022, 4:34pm UTC](https://meta.discourse.org/t/problem-with-post-revisions-after-updating-to-2-8-6-stable-or-2-9-0-beta7/232885/5 "2022-07-14T16:34:11Z")
I’ve had a quick look at the links you shared and it seems that the posts with missing edit revisions are the ones that also have the dates in the topic header. Do you have a theme component that adds those?
---
### Author:  [@mentalstring](https://meta.discourse.org/u/mentalstring)
#### Post date: [July 14, 2022, 4:43pm UTC](https://meta.discourse.org/t/problem-with-post-revisions-after-updating-to-2-8-6-stable-or-2-9-0-beta7/232885/6 "2022-07-14T16:43:16Z")
Unsure if you mean the topic title or something else. The topic tiles, despite their look, are manually added. Although, yes, both posts with problem seem to happen within a common parent category which is where people organize meetings.
We do run the [paviliondev/discourse-events](https://github.com/paviliondev/discourse-events) plugin and topics on this category do have an associated event on the first post (which is where this problem is happening). However, using the safe-mode to disable the plugin didn’t seem to make the revisions work again.
Anything else I could try?
---
### Author:  [@david](https://meta.discourse.org/u/david)
#### Post date: [July 14, 2022, 4:49pm UTC](https://meta.discourse.org/t/problem-with-post-revisions-after-updating-to-2-8-6-stable-or-2-9-0-beta7/232885/7 "2022-07-14T16:49:07Z")
I think this must be related to [SECURITY: Bump Rails to 6.1.6.1 (stable) (#17470) · discourse/discourse@bb287c6 · GitHub](https://github.com/discourse/discourse/commit/bb287c6c74aed9c9ccd36f6270c219f806bb84f3). I’m looking through some of our own sites right now and it seems like we have a few similar error logs. Will get it fixed up and update here when it’s fixed 👀
---
### Author:  [@david](https://meta.discourse.org/u/david)
#### Post date: [July 15, 2022, 12:00am UTC](https://meta.discourse.org/t/problem-with-post-revisions-after-updating-to-2-8-6-stable-or-2-9-0-beta7/232885/10 "2022-07-15T00:00:34Z")
This should be fixed by [FIX: Allow Time objects to be deserialized in PostRevision (#17501) · discourse/discourse@7d9b98a · GitHub](https://github.com/discourse/discourse/commit/7d9b98a1614c48905df129b8691a07a834fa12f7)
and on the stable branch [FIX: Allow Time objects to be deserialized in PostRevision (stable) (… · discourse/discourse@5d2ecce · GitHub](https://github.com/discourse/discourse/commit/5d2ecce3f6e1064c8053c69d2a85def79d8004a3)
To update a [standard install](https://meta.discourse.org/t/142537?silent=true), visit `/admin/upgrade`
---
### Author:  [@darkpixlz](https://meta.discourse.org/u/darkpixlz)
#### Post date: [July 15, 2022, 1:40am UTC](https://meta.discourse.org/t/problem-with-post-revisions-after-updating-to-2-8-6-stable-or-2-9-0-beta7/232885/11 "2022-07-15T01:40:08Z")
I am still getting this issue, after upgrading.
It’s more occasional, but it still happens every now and then.
---
### Author:  [@mentalstring](https://meta.discourse.org/u/mentalstring)
#### Post date: [July 15, 2022, 10:51am UTC](https://meta.discourse.org/t/problem-with-post-revisions-after-updating-to-2-8-6-stable-or-2-9-0-beta7/232885/12 "2022-07-15T10:51:15Z")
Thank you for the quick work on this. But I fear it hasn’t fixed it for us. The two posts I mentioned still behave the same way, with no visible versions. Tried both `/admin/upgrade` and rebuilding it.
---
### Author:  [@david](https://meta.discourse.org/u/david)
#### Post date: [July 15, 2022, 10:56am UTC](https://meta.discourse.org/t/problem-with-post-revisions-after-updating-to-2-8-6-stable-or-2-9-0-beta7/232885/13 "2022-07-15T10:56:31Z")
Sorry about that! This fix did help with the similar errors we were seeing on our hosting, so there must be something extra at play on your site. Most likely plugin/import related.
Please can you visit `/logs` and look for any errors like
```plaintext
Psych::DisallowedClass (Tried to load unspecified class: Time)
```
The “Time” version is the only one we were seeing, and should now be resolved. What other ‘unspecified class’ errors do you see in your logs?
---
### Author:  [@mentalstring](https://meta.discourse.org/u/mentalstring)
#### Post date: [July 15, 2022, 11:06am UTC](https://meta.discourse.org/t/problem-with-post-revisions-after-updating-to-2-8-6-stable-or-2-9-0-beta7/232885/14 "2022-07-15T11:06:07Z")
Ah, so maybe not the the same problem then.
All the `Psych::DisallowedClass` errors we have been seeing are about class `unspecified class: Symbol`, as per backtrace posted earlier.
I tried disabling the events (from [paviliondev/discourse-events](https://github.com/paviliondev/discourse-events) plugin) on that particular category, but that alone didn’t seem to make a difference.
Does the error above give any hint before I go the route of trying to disable the plugin forum wide (which will require rebuilds)?
---
### Author:  [@david](https://meta.discourse.org/u/david)
#### Post date: [July 15, 2022, 11:13am UTC](https://meta.discourse.org/t/problem-with-post-revisions-after-updating-to-2-8-6-stable-or-2-9-0-beta7/232885/15 "2022-07-15T11:13:59Z")
Unfortunately I don’t think disabling the plugin will make any difference. The problematic data is already stored in the database, so it’s there to stay. I think we can safely add `Symbol` to the list of allowed classes. I’ll do that 👀
Edit: to be clear, this isn’t really the plugin’s fault. Previously, any data type was allowed to be stored in the PostRevision. The Rails security issue means we’ve had to suddenly change the behaviour and limit the allowed data types.
---
### Author:  [@david](https://meta.discourse.org/u/david)
#### Post date: [July 15, 2022, 12:16pm UTC](https://meta.discourse.org/t/problem-with-post-revisions-after-updating-to-2-8-6-stable-or-2-9-0-beta7/232885/16 "2022-07-15T12:16:52Z")
Please can you try updating again @mentalstring - I just pushed [FIX: Allow Symbol objects to be deserialized in PostRevision (stable)… · discourse/discourse@f0ef186 · GitHub](https://github.com/discourse/discourse/commit/f0ef186a4e557abbd5c20332ca41f201139b1920)
---
### Author:  [@mentalstring](https://meta.discourse.org/u/mentalstring)
#### Post date: [July 15, 2022, 12:26pm UTC](https://meta.discourse.org/t/problem-with-post-revisions-after-updating-to-2-8-6-stable-or-2-9-0-beta7/232885/17 "2022-07-15T12:26:23Z")
That was it — it’s working as expected now! 👍
Thank you for looking into this so quickly.
---
### Author:  [@darkpixlz](https://meta.discourse.org/u/darkpixlz)
#### Post date: [July 15, 2022, 3:13pm UTC](https://meta.discourse.org/t/problem-with-post-revisions-after-updating-to-2-8-6-stable-or-2-9-0-beta7/232885/18 "2022-07-15T15:13:00Z")
Hey, this still doesn’t work after the update.
---
### Author:  [@david](https://meta.discourse.org/u/david)
#### Post date: [July 15, 2022, 3:28pm UTC](https://meta.discourse.org/t/problem-with-post-revisions-after-updating-to-2-8-6-stable-or-2-9-0-beta7/232885/19 "2022-07-15T15:28:58Z")
@darkpixlz please can you follow these steps and let us know what you find:
> [@david](#):
>
> Please can you visit `/logs` and look for any errors like
>
> ```plaintext
> Psych::DisallowedClass (Tried to load unspecified class: Time)
>
> ```
>
> The “Time” version is the only one we were seeing, and should now be resolved. What other ‘unspecified class’ errors do you see in your logs?
---
### Author:  [@darkpixlz](https://meta.discourse.org/u/darkpixlz)
#### Post date: [July 15, 2022, 3:31pm UTC](https://meta.discourse.org/t/problem-with-post-revisions-after-updating-to-2-8-6-stable-or-2-9-0-beta7/232885/20 "2022-07-15T15:31:08Z")
I only see this stuff.
---
### Author:  [@david](https://meta.discourse.org/u/david)
#### Post date: [July 15, 2022, 3:37pm UTC](https://meta.discourse.org/t/problem-with-post-revisions-after-updating-to-2-8-6-stable-or-2-9-0-beta7/232885/21 "2022-07-15T15:37:48Z")
Hmm ok, looks like you have errors for `User` and `Group`. Can you share a list of plugins which are installed on the site?
---
### Author:  [@darkpixlz](https://meta.discourse.org/u/darkpixlz)
#### Post date: [July 15, 2022, 3:43pm UTC](https://meta.discourse.org/t/problem-with-post-revisions-after-updating-to-2-8-6-stable-or-2-9-0-beta7/232885/22 "2022-07-15T15:43:57Z")
Plugins:
Discourse-Akismet
Discourse Apple Login
Discourse BCC
Discourse Cakeday
Discourse Calendar
Discourse Chat
Discourse Custom Wizard
Discourse follow
Discourse Gamification
Discourse Mate
Discourse Microsoft login
Discourse ImgFlip
Discourse Promethehus
Discourse Ratings
Discourse Solved
Discourse Spoiler
Discourse Steam Login
Discourse Tickets
Discourse Userr Network
Discourse User Notes
Discourse Voting
Discourse QA
Discourse Who’s online
Discourse Yearly Review
Discourse Manager
Styleguide
I can get components if you want
---
### Author:  [@crcoli7307](https://meta.discourse.org/u/crcoli7307)
#### Post date: [July 15, 2022, 4:16pm UTC](https://meta.discourse.org/t/problem-with-post-revisions-after-updating-to-2-8-6-stable-or-2-9-0-beta7/232885/23 "2022-07-15T16:16:38Z")
> [@darkpixlz](#):
>
> Discourse-Akismet
> Discourse Apple Login
> Discourse BCC
> Discourse Cakeday
> Discourse Calendar
> Discourse Chat
> Discourse Custom Wizard
> Discourse follow
> Discourse Gamification
> Discourse Mate
> Discourse Microsoft login
> Discourse ImgFlip
> Discourse Promethehus
> Discourse Ratings
> Discourse Solved
> Discourse Spoiler
> Discourse Steam Login
> Discourse Tickets
> Discourse Userr Network
> Discourse User Notes
> Discourse Voting
> Discourse QA
> Discourse Who’s online
> Discourse Yearly Review
> Discourse Manager
> Styleguide
Aka, we have pretty much every plugin that’s functional 🤣
[Next page](https://meta.discourse.org/t/problem-with-post-revisions-after-updating-to-2-8-6-stable-or-2-9-0-beta7/232885.md?page=2)